As someone once said, the greatness of a scientist can be measured by the extent to which they retard future research. John Snow is thus a great man indeed, and has just had by popular acclaim a fulsome belated obituary in The Lancet. However, a major criterion for a scientific breakthrough is that it must be independently replicated. So why cannot I find a single subsequent example of cholera due to drinking water? I have asked several experts, and they have not been able to direct me to any such study.
See Max von Pettenkofer Practitioner 1877;18:135,204 for what I think is still the best review of the epidemiology of cholera.
Yes, even bottled water can transmit cholera. Read Paul Blake's chapter 'Cholera for a Dime' in Dworkin MS (ed) Outbreak Investigations Around the World: Case Studies in Infectious Disease Field Epidemiology, Jones & Bartlett, 2009.
Yes, even bottled water can transmit cholera. Read Paul Blake's chapter 'Cholera for a Dime' in Dworkin MS (ed) Outbreak Investigations Around the World: Case Studies in Infectious Disease Field Epidemiology, Jones & Bartlett, 2009.
Sorry, I forgot to mention that there was indeed one example (in Portugal,1974) of an epidemic spread via bottled water. But is this really a replication of Snow?
So, where are the others?
Two years ago a cholera epidemic occurred in central parts of Iran. The most important way of infection was polluted water and then groceries watered by waste water. A study conducted to this epidemic but unfortunately the article is in Farsi.
Cholera, dysentery, typhoid, etc., are more likely to occur due to deficiency of proper sanitation and hygiene. The recent outbreak of cholera in Haiti is a evidence of it. Where cholera is not recorded since the last 100 years, but after experiencing an
earthquake in January 2010, about half-a-million cholera cases and more than 6,500 cholera related deaths were reported within a year, (see, http://www.cdc.gov/haiticholera/haiti_cholera.htm ). As the earthquake hit the country, Haitians were
compelled to live in camps under unhygienic conditions and were bound to consumed water from the sources contaminated with V. Cholerae (a pathogen responsible for cholera infection). Basically, cholera spread via multiplication transmission pathways, as shown in the given figure.
Where sanitation is poor or breaks down, it is sometimes difficult to sort out the 'source' the cholera ingestion, be it food or water, because both are contaminated. Here's a case where contaminated water lead to contaminated food and a multi-person epidemic of infection in the USA:
N Engl J Med. 1983 Sep 1;309(9):523-6.
Cholera on a Gulf Coast oil rig.
Johnston JM, Martin DL, Perdue J, McFarland LM, Caraway CT, Lippy EC, Blake PA.
Abstract
A single case of severe diarrhea on a floating Texas oil rig was followed two days later by what proved to be the largest outbreak of cholera in the United States in over a century. After isolation of toxigenic Vibrio cholerae El Tor Inaba of the typical United States phage type from the index patient's stool, the ensuing investigation detected 14 additional cases of cholera and one asymptomatic infection serologically. Infection was associated with eating rice on the oil rig on a particular day (P = 0.03) when an open valve permitted the rig's drinking-water system to be contaminated by canal water containing sewage (including that from the index patient) discharged from the rig. The rice had been rinsed in the contaminated water after cooking, and before being served it had been maintained at a temperature that allows V. cholerae 01 to multiply. Toxigenic V. cholerae 01 is persisting in the United States, and large common-source outbreaks of cholera can occur if proper sanitation is not maintained.
"Where sanitation is poor or breaks down, it is sometimes difficult to sort out the 'source' the cholera ingestion, be it food or water, because both are contaminated"
Precisely the problem, as illustrated by the above answers:
Ali, I accept that cholera can be spread via infected foods, rice, salads, etc. If there was clear evidence that spread was unambiguously via drinking water, the study should be published in a major English journal.
Charles, the conclusion from the oil rig outbreak looks reasonable, but it is not a replication of Snow's study.
Vishal, thanks for the diagram, which makes my point perfectly!
There are plenty of clear examples of epidemics of gastroenteritis traced to contaminated water or milk supplies for many different organisms, but not for cholera. Quoting references for outbreaks where multiple modes of transmission are conceded does nothing to clarify the situation, and in fact only confirms my suspicion that if there were a definite example of a single-source outbreak from drinking water someone would have posted it by now. This is one occasion, after one and a half centuries, where absence of evidence is evidence of absence.
I think you should read a little more broadly.
First, it takes a large inoculum ( ~ 10^6 bacilli) on average to cause a case of cholera, so a common source exposure does not always translate into disease.
Second, before the advent of chlorination (or other antiseptic) water treatments, contaminated water was often a source of cholera in outbreaks during the 19th century across the US and Europe. John Snow's major epidemiological work was not the Broad Street pump outbreak, but rather his linking of one London water company to cholera outbreaks all over London over a multi-year period.
With the decline of outbreaks following water treatment in the developed world, it was accepted that water had been a pathway for infection, and the with the problem solved, the issue was no longer an issue for research.
The bottled water outbreak in Portugal and the oil rig outbreak outbreak in the USA graphically illustrate the potential for waterborne cholera transmission when sanitation breaks down. I would call these CDC studies high-quality evidence. So there is no 'absence of evidence', but rather a poorly studied problem in the developing world, and what appears to be settled evidence in the developed world.
If water untreated or people unhygiens so cholera can be transmitted through the contaminated acording to chain of infection
1. "I think you should read a little more broadly."
I accept I have not read the thousands of reports of cholera outbreaks in the 19th C, many of high quality, but I am sure von Pettenkofer was extremely familiar with these, and I have read his reviews. Had there been any showing that it was spread through drinking water, surely these would have been pointed out to him before he drunk the infamous cholera cocktail? I do not promise to read all these old reports, but if a reference is provided for just one that shows the drinking water supply was the primary and sole source of the disease, as maintained by Snow, I will read it.
2. " it was accepted that water had been a pathway for infection, and the with the problem solved, the issue was no longer an issue for research."
I am not sure that Haitians will be satisfied with this state of affairs.
3. " I would call these CDC studies high-quality evidence."
Yes, but the problem is not with the evidence, but the inferences therefrom. It is agreed that the seawater is a natural reservoir for vibrios, but is the dose from directly ingesting water sufficient to induce cholera? A secondary intermediate amplification system may be needed, eg incubation in warm rice.
4. "With the decline of outbreaks following water treatment in the developed world, it was accepted that water had been a pathway for infection".
Measles and TB have also declined.
Any water if contaminated with Vibrio cholerae O1 or O139, it can cause cholera.
Sujit K. Bhattacharya. India
"Any water if contaminated with Vibrio cholerae O1 or O139, it can cause cholera"
Yes it could, but does it? Only epidemiological evidence will resolve this. Pettenkofer knew far more than me about this, and he thought it did not, at least directly by ingestion of water. If there are people around today who know more than von P about his, can they please unmask themselves?
Of course the individual must be susceptible; the infecting dose is 10 to the power 9 organisms. Those with achlorhydria suffer more. Blood group "O" more susceptible.
From Med Times Gazette 1868;1:459
"Letheby...believed that in the official investigations .. those conducting them had been guided by coincidences, and nothing more; and he protested against the adoption of a foregone conclusion which tended to stop all further inquiry. No fact had been alleged to prove the connexion of cholera with the East London water, while the exceptions of Stamford-hill and other places were alone sufficient to prove the fallacy of the water theory. As to the conclusions of the General Board of Health, he regarded them with the greatest suspicion; they all rested on preconceived notions. The conclusion that the water supply of East London originated the outbreak in that quarter was first adopted by the Registrar-General, and then all the facts were examined and discused from that point of view alone. It was to put an end to this unscientific mode of investigation that he had raised his voice" [in front of the Medical Officers of Health].
This is exactly the point I have been trying to make. Nothing has changed over the last 146 years, other than that notions have become even more preconceived.
If cholera is spread via fecally-contaminated drinking water, it would help if direct contact with feces was harmful. This is another preconceived notion that may not be true:
"During the severe visit of cholera to the native city of Indore, in 1864, I noticed that attacks of the disease were very unfrequent amongst the class of men and women whose duties brought them into immediate relation with the sick. The 'bhunjies', or caste whose work is cleansing and removing excreta merely, suffered but very little from attacks of the disease...As a class they are not cleanly, and being engaged in hourly and continued contact with what has been considered the very poison itself -- vomit and excreta -- it is, to say the least, a curious fact tending somewhat to shake the doctrine of contagion".
Pope JJ Brief sanitary notes from practical experience, more especially in reference to cholera Journal of Social Science 1866 598-606.
How is Cholera Spread?
Cholera germs are found in the feces (poop) of infected people.
Cholera is spread when feces (poop) from an infected person gets into the water people drink or the food people eat.
Cholera is not likely to spread directly from one person to another.
http://www.cdc.gov/cholera/prevention.html
"Cholera is spread when feces (poop) from an infected person gets into the water people drink or the food people eat"
I agree that there are well documented epidemics traced to contaminated foods, but cannot find any linked to drinking water (other than a possible European outbreak from bottled water). Does the ICDD have details of any such examples (as opposed to rhetoric)?
The International Center for Diarrhoeal Diseases Research, Bangladesh has many publications and research on cholera in the developing countries. For more information check: www.icddrb.org
This is an interesting discussion.Technically cholera vibrio or any other bacteria for that matter should not be transmitted by treated water(drinking water) because of the presence of chlorine in the drinking water. The break-point chlorination allows the chlorine to act on all bacteria and so technically there should be no bacteria.in drinking water and so cholera should not be transmitted by drinking water, yet studies have shown that drinking water can transmit cholera. .I witnessed a cholera out break in Malaysia many years ago. (The 1978 Cholera outbreak in Krian district published in Malaysian Medical Journal 1981 Sept 36(3):129-35). In this outbreak drinking water was partly responsible for the outbreak due to the leakages in the pipes supplying water in the peripheral areas. The chlorine was 0.1 ppm and I requested the authorities to raise the chlorine level to 0.5 ppm to overcome the epidemic but the person in charge of water at that time said that there was no necessity since there is chlorine present in the water (0.1 ppm) and there fore no bacteria. If drinking water has enough chlorine then can cholera still be transmitted?
"The International Center for Diarrhoeal Diseases Research, Bangladesh has many publications and research on cholera in the developing countries. For more information check: www.icddrb.org"
I could not find the relevant information on the above website. All I am asking for is a single good replication study of Snow from a leading English language journal. Five months later I am still waiting. I will be reading MMJ 1981;36:129, but given that the water supply is said to be only partly responsible, I do not expect this to be conclusive. Also, if this definitively implicated the water supply, why was it not reported in an international journal?
Here is an extract from an ICDDR study on cholera in children recently published in a top journal, PLoS ONE 2013;8:e54395:
"The general lack of association of water and sanitation variables with cholera risk was surprising given the importance of water in cholera transmission. Rather than a true lack of association, it’s possible that our null results reflect the limitations of using self-reported water and sanitation measures, which may be unreliable".
I am surprised that they were surprised. The simplest explanation, of course, is that there is no true association.
I put up this question because I had the impression of an absence of epidemiological evidence in support of Snow's drinking water theory, and suspected this was one case where this constituted evidence of absence. I knew of von Pettenkofer's failed attempt to give himself cholera, but had no idea so many others had also tried and failed. See this extract from Howard-Jones WHO Chronicle 1974:
" Elie Metchnikov reported
a similar experiment on himself in which, after first
neutralizing his gastric juices with sodium bicarbonate
he swallowed an emulsion of part of a culture
of a vibrio from Hamburg in sterile broth. His
laboratory technician, Latapie, made the same experiment.
Neither had any symptoms, nor could
they discover vibrios in their stools. A week later,
they both repeated the experiment, but both suffered
no worse result than borborygmi and a slight
malaise on the sixth day. On that day they both
swallowed part of a culture of vibrios, as also did
a third person identified only as " Gr. ". During the
next few days, both Metchnikoff and Latapie had a
tendency to constipation, the latter developing a
slight diarrhoea on the ninth day. In the stools of
neither were vibrios detectable. Gr., on the other
hand, had frequent loose stools that gave on gelatine
plates " only a pure culture of comma bacilli ",
but after six days he was again " absolutely normal
". Metchnikoff cites a number of other examples
of experimental infection in human subjects,
including those initiated by Hasterlik of Vienna....
By 1894, Drasche of Vienna was able to cite 27
experiments on themselves by 21 different persons,
of which 10 had been positive in the sense that
varying degrees of diarrhoea had resulted, and 17
had been negative. In most of the positive cases
and a few of the negative, comma bacilli had been
found in the stools. Drasche concludes: " With the
results of the auto-infection experiments the bacillary
cholera question is not settled."
Surely this is conclusive evidence against the drinking-water theory?
Addendum: Or, why should homeopathic doses of vibrio in drinking water induce cholera when pure cultures do not? As EM put it (Ann de l'Inst Pasteur 1893;7: 403):
"Dans an assez grand nombre d'experiences sur l'homme, l'effet du vibrion de Koch a donc ete ou nul ou insignificant, si on le compare avec la gravite du vrai cholera asiatique."
"I witnessed a cholera out break in Malaysia many years ago. (The 1978 Cholera outbreak in Krian district published in Malaysian Medical Journal 1981 Sept 36(3):129-35). In this outbreak drinking water was partly responsible for the outbreak due to the leakages in the pipes supplying water in the peripheral areas."
This study gives no support to the water-borne theory since
1. There was no mention of leaking pipes.
2. The first fortnight of the outbreak did correspond to a lowish chlorine level in the Public Water Supply. But how could this have become grossly contaminated before the first case of cholera?
3. There were 2 positive water samples one from a pond and one from a house, but none from the water supply, source reservoir, canals, sea or rivers.
4. "The epidemic spread over 6 incubation periods. It suggests a multiple foci and multiple exposure type of epidemic."
There was a serious cholera epidemic in Egypt in 1947. Some of the data and investigations on this were published in J Roy Egypt Med Assoc 1948 Vol 31. Some clear conclusions could be drawn, many quite inconsistent with the drinking water hypothesis:
1. 90% of case were attributed to contaminated foods (dates, seafood, fruit, veg, bread, etc).
2. In provinces where infected foods were the main vehicle, 754 out of 835 villages were infected; in provinces where the water supply was contaminated, only 24 out of 540 villages were infected.
3. Contaminated water is supposedly a cause of infant diarrhea, yet only 2% of those under 1y were cholera carriers, compared to 10% of children aged 1-15y and 7% of adults.
4. The epidemic started in the delta, so did not spread downstream via the Nile.
5. Vibrios did not survive longer than a day in sea waters, but did so for many days longer in cleaner waters in the laboratory, implicating a natural antibacterial agent in the dirty waters. This casts doubt on the relevance of low chlorine levels in the Malaysia outbreak (see previous postings).
6. In the 1831 Egypt cholera epidemic, only one out 240 staff in the cholera hospitals caught cholera. They were likely exposed to far greater cholera doses there than via drinking water.
7. "It was conclusively proved that cholera transmission by contaminated food stuffs cannot take place unless the atmospheric humidity is 10mgm or a little more".
Yes to some extend cholera can be transmitted through drinking water.
The water has to be contaminated and other factors might facilitate clinical symptoms. In Nigeria for instances cholera outbreak usually occur where there is poor sanitation and hygiene and lack of portable drinking water and water used for other activities. And this cholera cases increase during floods and at the beginning of the rains
@ Anthony Gordon; You have spent much time refuting the theory that contaminated water contributes to the cause of Cholera. I would like to know what you think contributes to the cause? It is thought that no one questions conventional wisdom unless of course they have another theory or at least why the conventional school of thought is incorrect.
Anthony,
You wrote;
>
My understanding is that this is simply not true. Coastal and estuarine waters act as a significant reservoir for cholera.
See, for example;
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC161524/
.
This following passage may explain why the researchers in your old 1948 article believed otherwise. >
Paul.
At the risk of boring other readers (sorry folks) I am reproducing some extracts of a conversation Anthony and I had last year re cholera transmission vectors;
Having spent a bit of time in very poor countries where gastrointestinal infections are a leading cause of death, I find it very hard to understand why you would doubt that a water-borne disease that causes massive watery discharges from the sufferer can be easily transmitted in drinking water. Perhaps you believe (like many of Dr John Snow's contemparies) that infectious diseases are spread by "miasma"?
>
http://www.nichd.nih.gov/Pages/index.aspx
>
http://www.scielosp.org/scielo.php?pid=S0042-96862003000300010&script=sci_arttext&tlng=pt
.
Cholera is most often transmitted in developed nations from contaminated shellfish.
Cholera is most often transmitted in the developing world by faeces from an infected individual contaminating the drinking water.
http://www.ncbi.nlm.nih.gov/pubmed/14738797
.
http://www.who.int/mediacentre/factsheets/fs107/en/
.
http://www.cdc.gov/cholera/prevention.html
.
>
There is a very good discussion of cholera, (which mentions John Snow), based on the Haitian outbreak (referred to, above) here;
http://www.ph.ucla.edu/epi/snow/cholera_haiti.html
.
Unfortunately it appears that UN peace keeping forces stationed in Nepal, who were flown to Haiti in response to the humanitarian aftermath of the earthquakes, may have actually brought this strain of cholera with them. The disruption to sanitation and water supplies helped ensure that it spread. And many people, especially vulnerable infants, died as a result.
You appear to be quite lonely in your belief that cholera is not transmitted to infants via contaminated water. The fact that cholera rates are far higher amongst children in developing nations who are fed formula than infants who are breast-fed is uncontroversial.
Do you actually have any evidence to contradict this? Anthony, if you do, please link to it for us.
If you are a scientist, you should know that absence of evidence can never be presumed to indicate evidence of absence.
there is a very strong consensus that the Haitian outbreak has two possible origins.
One is that cholera dormant in the coastal waters exploded in population due to the extreme weather conditions, and that a break down of water supplies and sanitation services in the wake of the disaster helped it spread between humans.
The other is that it was carried to Haiti by some of the Nepalese Peace keepers, and the conditions mentioned above facilitated it's rapid dissemination.
The outbreak in Haiti was identified as Vibrio cholerae serogroup 01, serotype Ogawa, biotype El Tor by the National Laboratory of Public Health in Haiti and this genotypic identification was confirmed by the United States Centers for Disease Control and Prevention.
Exactly the same strain was responsible for the outbreak of Cholera in Nepal in late 2008 and 2009. The most recent cholera outbreak that occurred in Nepal was in Kathmandu, first cases reported on September 23, 2010, a fortnight before the troops left for Haiti, arriving between October 8 and 15, 2010.
In Haiti, the government reported the initial wave of cases on October 22, 2010 (a week after the Nepalese troops had arrived).
Some of the first cases occurred in Mirebalais (where the Nepalese peacekeeping troops were stationed), and others down-river in the Artibonite valley, and still others in communities by the coastal waters where the river ends. No initial cholera cases, however, appeared to be found up-river from Mirebalais, or in other neighbouring water-sheds, supporting the notion that the source came from the Mirebalais area.
A percentage of the human population are asymptomatic carriers of the disease. Some of the Nepalese troops may have acted as a vector for the disease without even realising that they had an infection.
It seems possible that the cholera was introduced accidentally by the Nepalese contingent, especially as it was the same strain of cholera reported in Nepal, and because infected people responded to the same antibiotics as were found effective in the outbreak in Nepal.
"The organism that is causing the disease is very uncharacteristic of (Haiti and the Caribbean), and is quite characteristic of the region from where the soldiers in the base came. ... I don't see there is any way to avoid the conclusion that an unfortunate and presumably accidental introduction of the organism occurred."
John Mekalanos, PhD, Professor and Chair of the Department of Microbiology and Molecular Genetics at Harvard University
Alternatively, the initial pattern of cases does not rule out a source in the coastal region, moving up-river to as far as Mirebalais via river transport and trade. As cholera can lie dormant in coastal waters for decades without human outbreaks, which typically occur when there are algal blooms or unusual weather conditions, there remains a possibility that the Nepalese connection is a coincidence.
The fact that we cannot know for sure which of these hypothesis is correct does not mean there is a lack of consensus amongst researchers and public health professionals about where the cholera may have come from, or how it subsequently spread.
While the general consensus appears to favour the Nepalese hypothesis, (see links below) we will never know for sure. Admitting that you don't, and often can't, know things with absolute certainty is the basic level of honesty required for scientific research.
Entertaining more than one possibility is not a failure, it is just good science.
.
http://www.ph.ucla.edu/epi/snow/CMI18_E158_E163_2012_Nepalese_origin_article.pdf
.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3030187/
.
Generally, most deaths from Cholera are in the 2 to 4 age-group.
I can't tell you how many infants have died so far from the ongoing Haitian epidemic, but there are figures for children under 5 here;
http://www.cidrap.umn.edu/cidrap/content/fs/food-disease/news/jan0913cholera.html
.
The two hypotheses are not diametrically opposed. They both are based on what is known of cholera, and what is known about the specific circumstances of this outbreak. They both accept that cholera is a water borne infection. The only difference is the suggested original source of the outbreak.
I did mention the hypothesis Colwell supports as one of two logical options, and said there was a possibility that the outbreak was not a result of the "Nepalese Connection."
For example, ballast water dumped by ships from Asia could easily have introduced that particular strain to coastal waters years, perhaps decades, before environmental conditions were right for an outbreak amongst the humans in Haiti.
As more than one strain of Cholera have been identified by Colwell's team, it is equally possible that BOTH the hypotheses I mentioned above are true.
>
http://www.npr.org/blogs/health/2012/06/18/155311990/scientists-find-new-wrinkle-in-how-cholera-got-to-haiti
.
It would be nice if you might occasionally provide links to the various studies/references/authorities you quote or allude to, old bean.
You just apologised for not providing links, while referring me to an article published in 1857?
Earlier you stated that >,
yet it seems you are not inclined to believe her when she makes a statement that contradicts your belief?
You write; >
It's pretty simple Anthony. People pump water in pipes and transport it in tanker trucks from place to place, and (most significantly) any infected people who travel up stream or across watersheds can spread the virus up stream or into different river systemns.
It was the fact that all of the initial cases took place in the town the Nepalese Peace Keepers were quartered in, or down stream of this town, combined with the timing, that suggested the Nepalese as an accidental transmission vector...
Here's Dr. Renaud Piarroux. He >
>>
http://www.ph.ucla.edu/epi/snow/cholera_haiti_newdev34.html
Max Joseph von Pettenkofer did indeed drink a cocktail containing cholera, (because he believed in a version of the miasma ("bad air") theory), and subsequently did not develop any serious symptoms.
All this really proves is that the you cannot draw meaningful conclusions from a study with a sample where n = 1.
I would suggest that the most likely explanation is that Pettenkoffer was a healthy, well nourished fellow from a country where the population had been under selection pressure from sporadic outbreaks of cholera for many generations, and that he either did not ingest a sufficient quantity of the bacteria to show any symptoms of diarrhea, or who was one of that percentage of any population who are immune asymptomatic carriers of cholera.
>
Cholera
The Lancet, Volume 363, Issue 9404, Pages 223-233
David A Sack, R Bradley Sack, G Balakrish Nair, AK Siddique
People with lowered immunity, and people who are malnourished, are much more susceptible.
http://www.who.int/cholera/technical/prevention/control/en/
.
As cholera had not been seen in Haiti for over a hundred years, the population were immunologically naive to the disease. I would expect a much lower percentage of their population would have had any natural resistance than the population of late 19thC Bavaria. I also suspect there is a much higher rate of malnutrition (and of HIV) in modern Haiti than amongst ennobled chemists/hygienists living in 19C Europe, Ist dieses nicht die meisten wahrscheinlich?
Regards to you Anthony, you love-able old contrarian! Hope you are well.
Paul.
Paul Dessauer,
After reading through your points (which are difficult to extract from your many editorial meanderings) I wonder:
Which of your many citations bear experiments/analyses that show, conclusively, that cholera is transmitted by drinking water?
I personally lean towards this conventional view (the same as yours) and I am a non-expert in this area (or epidemiology as a whole). But your arguments often seem to take the flavor/form of an appeal to authority:
"Here's Dr. Renaud Piarroux. He
Hi Ryan,
Thanks for your comments.Your point re: appeal to authority is well taken. I did warn in my second response that I was about to start simply cut-and-pasting extracts from a previous conversation with Anthony, and apologized in advance for the disjointed results.
In that original discussion, I linked to the interview with Dr. Renaud Piarroux in response to Anthony's appeal to the authority of Dr Rita Colwell, (despite the fact that latter in the same article he quoted she clearly contradicted Anthony's position).
In his initial question, Anthony states that he can not find a single example in the literature of cholera transmitted via drinking water, (post Dr John Snow), yet the very first answer he received (from Charles King) cites a well documented case of cholera transmitted via bottled drinking water. Anthony then says "Sorry, I forgot to mention that there was one case... " Someone who has dispassionately reviewed all of the available evidence should not "forget" a case that clearly refutes their hypothesis.
Later, Anthony states that;
> but his statement is based on a single article; a case-report written in 1948 describing an outbreak that occurred in the previous year.
It only takes a few seconds on Google-scholar to discover that Anthony's statement is now known to be completely untrue. In fact coastal and estuarine waters form a significant reservoir for cholera, which can lay dormant in these waters for decades, only emerging as an epidemic disease when there are algal blooms or unusually warm weather. (see link from my first post, above)
I would respectfully suggest that the fact that Anthony relies on a single article from the 1940s, written before we had the means to detect dormant cholera in sea waters, (where it turns out the organism is actually quite ubiquitous), and ignores or does not bother examining more recent research, is telling.
Anthony then cites the case of Von Pettenkoffer drinking a solution containing cholera and not subsequently displaying symptoms as though this is conclusive proof that cholera cannot be transmitted by drinking contaminated water. I trust my last post (above) explains sufficiently clearly why this is an unscientific argument?
When Anthony asked me how (if it were water-borne) cholera could travel upstream, or cross water-sheds into different drainage systems, I was surprised that I had to point out that people transport water either in their bodies, or in containers, or pumped through pipes. (Douglas Adams once quipped that humans were invented by water to transport it uphill).
The Haiti epidemic reinforces our assumption that cholera can be transmitted by drinking water- in the aftermath of the earthquake, with people living under canvas with poor sanitation, emergency supplies of water were trucked from the major river where the initial outbreak occurred to neighboring watersheds, and so the disease spread. See references linked to above, and below.
The consensus of epidemiological and medical opinion is that cholera in developed nations is most often transmitted via contaminated bottom-feeding shellfish, and that in developing nations it is most often transmitted via contaminated water (either directly as drinking water, or because it is used to wash food that is then ingested). While we should be cautious of argument from authority, I am not invoking some eternal unchanging biblical authority here. The hypothesis is plausible given what we currently know about the disease and the organism that causes it. And the most effective response to an outbreak is to behave as if the disease is spread via contaminated water. While we cannot conduct an RCT, we have countless naturalistic experiments that confirm the hypothesis, and Anthony has yet to cite a cholera outbreak which cannot most easily be explained by this hypothesis. In fact the first such experiment was Dr John Snow's much more rigorous (but less famous) work during the second (1854-55) outbreak in London. Two companies supplied water to Lambeth, one with it's intake pipes upstream from the sewage outlets, one downstream. To his credit Snow recognised the opportunity this offered and mapped the distribution of water from each source, then plotted it against cholera cases in the district;
http://www.thelancet.com/journals/lancet/article/PIIS0140673613608302/images?imageId=fx2§ionType=lightBlue&hasDownloadImagesLink=false
.
In the question that heads this discussion, Anthony describes Dr John Snow as someone who "retarded future research" and this is a gross misrepresentation of the historical facts. Snow not only pioneered the safe use of anesthesia in surgery, he was one of the most vocal exponents of the "germ theory" of infectious disease in Britain when most medicos were still attributing communicable diseases to "bad air." His later work on Cholera in the second outbreak of 1854-55 is one of the foundations of modern statistical epidemiology.
This, (and the comments I've made in my post just above), are just some of the reasons why I address Anthony as a contrarian.
Anthony and I have met in quite a few online conversations on many other topics, and we get on quite well (I think? Don't we Anthony?). I do value and enjoy having my presumptions, prejudices and preconceptions challenged. However Anthony relies very heavily on extremely old journal articles (which he accesses as hard copies at the library he works in) and appears unwilling or unable to examine more up to date evidence. Perhaps he would like to comment about this?
You pose a great question Ryan, in your last paragraph, when you write;
>
We should indeed question unfounded beliefs. I'd suggest that my most primary assumption is that organizations such as the CDC, WHO, and MSF have not only thoroughly reviewed the evidence but also have enough practical experience of actually managing cholera epidemics to know more about it's transmission vectors than I do, or you do, or Anthony does.
http://www.ph.ucla.edu/epi/snow/Plos10%284%29_e1003967_Apr2014.pdf
.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2813%2960830-2/fulltext
.
Regards,
Paul.
"It is thought that no one questions conventional wisdom unless of course they have another theory or at least why the conventional school of thought is incorrect."
True enough I think, but no one is going to take any notice of my theories as long as they think conventional explanations are adequate.
I got into the cholera story in a roundabout way. I worked out, at least to my satisfaction, that the main cause of high infant mortality was latent otitis media, due mainly to supine feeding allowing a protected culture medium in the middle ear for respiratory organisms. It was then no longer necessary to suppose that infant diarrhea was due to contaminated oral intake (foods, milk, water), and when I looked at the literature critically, was surprised to find there was no good evidence to back up this conventional wisdom, including for cholera in infants. I then looked at cholera more generally, and was again surprised to find Snow's study has never been replicated.
"I would like to know what you think contributes to the cause?"
There are good epidemiological studies relating cholera to contaminated food, including seafood, in adults. The more I read about the epidemiology of cholera, the more baffled I become, and the more frustrated about how complacent experts are about making clear deductions from it. I think epidemics of cholera are due to spread via aerosols, but have not been able to conclusively nail down this mechanism yet. However, I feel confident that somewhere amongst the vast old literature there are vital or even conclusive clues.
"You wrote; > My understanding is that this is simply not true. Coastal and estuarine waters act as a significant reservoir for cholera." My quote referred to in vitro experiments, and was not relevant to the natural reservoir of vibrio in some coastal waters. My summary stated: "5. Vibrios did not survive longer than a day in sea waters, but did so for many days longer in cleaner waters in the laboratory, implicating a natural antibacterial agent in the dirty waters." So, their methods were sensitive enough to detect vibrios added to clean laboratory water.
"I find it very hard to understand why you would doubt that a water-borne disease that causes massive watery discharges from the sufferer can be easily transmitted in drinking water."
The operative word here is "can". It sounds deceptively plausible, it is only when you look at the evidence that the case collapses. It could transmit, but does it? It is quite clear that nurses, doctors and attendants on cholera wards do not catch the disease there, so why should they then be susceptible to homeopathic concentrations of vibrios from the drinking water supply?
"Cholera is most often transmitted in the developing world by faeces from an infected individual contaminating the drinking water."
I realise this is the accepted wisdom, but I would like to see the empirical data behind this.
"Some of the first cases occurred in Mirebalais (where the Nepalese peacekeeping troops were stationed), and others down-river in the Artibonite valley, and still others in communities by the coastal waters where the river ends. No initial cholera cases, however, appeared to be found up-river from Mirebalais, or in other neighbouring water-sheds, supporting the notion that the source came from the Mirebalais area"
From Med Times 1848;18;366
"It has been said that the epidemic travelled up the Volga, and that it generally follows the channels of rivers, as if running water exerted some peculiar influence over its dissemination. It is curious, however, that, even according to the lucubrations of the supporters of this notion, the pestilence marches against the stream instead of with its course...The disease generally breaks out first on the flat, swampy lands surounding the mouths of large rivers, or the low miasmatic banks of lakes and inland gulfs."
G’day Anthony;
You write;
Okay, so, for purposes of this discussion, let’s just take it as read that your hypothesis is correct, and that ear infections, not alimentary ones, are responsible for diarrhoea; you go on to write;
>
Assuming, just on your say-so for now, that your hypothesis is correct, are you suggesting that there can only be one aetiology responsible for all cases of infant diarrhoea globally? Is it really a case of “either/or” explanations?
>
If the cholera were truly at “homeopathic concentrations” no one would contract an infection at all. The point is that cholera can lie dormant and unnoticed in low concentrations for decades, and only emerges as an epidemic when there is unusually hot weather. And why don’t medical professionals get sick as often as family members?
I’ll quote Dr Piarroux again;
>
http://www.ph.ucla.edu/epi/snow/cholera_haiti_newdev34.html
.
Of cholera reservoirs in coastal waters, you wrote;
>
But they only detected it for a few days. Now that we can test for traces of DNA using PCR, we know that cholera can lie dormant at very low concentrations in sea water for decades and still flare up as an epidemic.
Why persist in quoting an article from the mid 19thC, which is examining survival of cholera in water in vitro in a lab, when I have already referred you to a more recent article in which cholera is detected “in the wild” in coastal waters all over the world?
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC161524/
.
You finally offer us a hint towards your own hypothesis;
>
Are you suggesting that cholera is an airborne infection? If the symptoms included coughing and sneezing, this might be reasonable. But they don’t. The symptoms are watery diarrhoea, leading to dehydration, which makes this idea implausible.
Your idea about aerosols is interesting to me for a different reason, however; cholera outbreaks often follow tropical storms.
This is attributed to higher temperature and humidity leading to a sharp increase in the ppm numbers of cholera vibrios in the water, heavy rains flooding water tables, overflowing sewers or latrines and leaving standing water, and to subsequent transmission amongst displaced people living in unsanitary conditions with storm damage to sanitation and water supply infrastructure etc. However you’ve just made me think that as a tropical storm builds and then approaches, the population of cholera in coastal and estuarine waters would explode in the warmer conditions, and then the storm surge and high winds would whip up frothy waves and carry droplets of highly infectious water far inland. If these droplets landed in bodies of warm but un-infected water, the cholera would rapidly colonise them.
You quote an article from 1848;
You continue to claim there is a lack of clear evidence to support Snow’s hypothesis, even when you have been referred by Charles H King to a study by Paul Blake that documents an outbreak transmitted by bottled drinking water,
Here’s a link to that document. See chapter 3, p37 (p67 of this PDF:
http://agus34drajat.files.wordpress.com/2010/10/outbreak-investigations-around-the-world-case-studies-in-infectious-disease-field-epidemiology.pdf
.
Was Blake's investigation convincing? Before this study the CDC recommended that travelers in areas affected by cholera outbreaks should drink bottled water. After this study they changed the recommendation to state you should only drink carbonated bottled water.
While we cannot conduct an RCT, we have countless naturalistic experiments that confirm the hypothesis that cholera can be transmitted by drinking contaminated water, (as well as by ingesting contaminated shell fish, or foods that have been washed with contaminated water, or by close physical contact with infected people).
Anthony, as yet you have not cited a single cholera outbreak which cannot most easily be explained by this hypothesis.
In fact the first such naturalistic experiment was Dr John Snow's much more rigorous (but less famous) work during the second (1854-55) outbreak in London. Two companies supplied water to Lambeth in 1849, and both had their intake pipes downstream from sewage outlets. During the interval between the 1849 outbreak and the 1854 outbreak, one of these companies moved its intake pipes upstream from the sewage outlets, while the second company left its pipes downstream of the effluvia outlets. To his credit Snow recognised the opportunity this offered and mapped the distribution of water from each source, then plotted it against cholera cases in the district, comparing the geographic incidence of the two epidemics;
http://www.thelancet.com/journals/lancet/article/PIIS0140673613608302/images?imageId=fx2§ionType=lightBlue&hasDownloadImagesLink=false
The two outbreaks closely correlated geographically to the available water sources- with areas where most households drew water from the second company’s pipes seeing a higher mortality rate in the second epidemic, but regions in which most households drew water from the company that moved their intake pipes showing a significant reduction in cholera incidence and mortality.
>
You might enjoy reading Snow’s text “On the Mode of Communication of Cholera” (published by J Churchill, 1855).
It's available for free in full here;
http://www.ph.ucla.edu/epi/snow/snowbook.html
.
Snow meticulously supports his hypothesis with a very large number of well investigated cases, amongst which he documents the famous instance of the Broad St Brewery, (where, in the midst of a raging cholera epidemic, not a single worker contracted the disease, (or at least none became symptomatic), presumably because of the combined facts that the brewery workers were provided free beer to drink all day, and that the brewery had its own deep well).
In addition you will find Snow recorded many other cases in which an outbreak hits all households in a street that draws its water from an infected source, but leaves one household untouched. Invariably this house sources its water from somewhere else.
eg: >
You have yet to cite a single case which can not be most easily explained by one of the feces or water-borne vectors acknowledged by the current consensus.
You have been provided with a well documented case in which drinking water was a major contributing vector to several outbreaks (just follow the link at the end of my previous post)
Snow's work, (just follow the link, at the start of this post) documents countless cases that conclusively support the hypothesis that cholera is water borne, and along the way Snow pioneered the investigative techniques that lay the foundation of all modern epidemiology, yet you accuse the poor fellow of "retarding future research."
What evidence can you offer to shake my faith in the current consensus of opinion?
Regards,
Paul.
"You have been provided with a well documented case in which drinking water was a major contributing vector to several outbreak"
"along the way Snow pioneered the investigative techniques that lay the foundation of all modern epidemiology"
I thought a fundamental tenet of modern epidemiology was that you do not rely on any single investigation or author. And in science in general, any important observation needs replication, ie independent confirmation. So I think detailed discussion of Snow's work is beside the point. It was ambiguous at best, so let us see if it can be replicated with far better modern methods, data and technology.
"What evidence can you offer to shake my faith in the current consensus of opinion?"
I was hoping RG was a faith-free zone.
Thanks, Paul, for contributing to what should be an important debate to many in the world today. Despite serious distraction from sport at the moment, I will be addressing other outstanding points on this topic in due course.
Thanks Anthony.
You wrote;
>
The first article I referred you to (above) is quite independent of Snow's writings.
This article was referenced by Charles King in the very first response to your question. Have you bothered to read it yet?
It's the study by Paul Blake that documents his investigation of outbreaks in Portugal in 1974.
The outbreaks were traced to several different sources, but many people were infected by drinking water from spigots at contaminated springs, or by drinking uncarbonated water bottled at those springs
Here’s the link to that document again. See chapter 3, p37 (p67 of this PDF:
http://agus34drajat.files.wordpress.com/2010/10/outbreak-investigations-around-the-world-case-studies-in-infectious-disease-field-epidemiology.pdf
,
Regards,
Paul.
"The outbreaks were traced to several different sources"
Which makes it very difficult to draw any conclusions about the relevance of one particular source. I read the study many years ago, and should have mentioned it at the beginning. However, one study where bottled water was implicated does not get us very far in considering if cholera is spread via the public water supply.
Here are some conclusions from the Portuguese study:
"Our investigations contributed to scientific knowledge about transmission
of cholera, including the most conclusive evidence ever presented that
cholera could be transmitted by shellfish contaminated before harvest, the
first reports that spring water contaminated before it emerges from the
ground can transmit cholera, and the first report that bottled uncarbonated mineral water can transmit cholera. Because investigators sometimes
focus on known vehicles and disregard possible vehicles that have not been
implicated previously, publishing this information may have saved lives... Dramatic advances...in understanding vehicles for cholera transmission have occurred since our investigations. Foods have proven to be more important vehicles than was thought previously and include raw and cooked seafood, cooked grains and legumes, and frozen coconut milk."
One really dramatic advance would have been replication of Snow's study!
"He is a major scientific authority on cholera epidemics, an expert in infectious diseases...
...People get sick by ingesting a high amount of the bacteria. This can be provoked by close contact with somebody suffering from cholera, but it’s easy to protect oneself from this kind of transmission by good hygiene. This is why medical staff rarely get ill despite the fact that they have numerous contacts with people suffering from cholera."
But has this expert read the many old reports from doctors who were in at the deep end? I have already put up on RG some of the many reports from often incredulous observers that close contacts of cholera patients did not catch the disease. Here is a comment from an Army doctor in Cawnpore in 1848, where I doubt that hygiene in general was up to modern medical standards (Med Times Gaz 1876;2:679):
"The hospital was never free of some cases, and at times it was crowded with them. The whole establishment may be said to have lived in the wards; the coolies for hours together never left the beds of the patients; the medical officers did nothing but administer to their wants: and yet not one man -- European, half-caste, or native -- ever showed the least symptoms of cholera. I took most particular care to have them mustered and looked at, but there was not in that year even a case of bowel complaint amongst them."
"Max Joseph von Pettenkofer did indeed drink a cocktail containing cholera, (because he believed in a version of the miasma ("bad air") theory), and subsequently did not develop any serious symptoms.
All this really proves is that the you cannot draw meaningful conclusions from a study with a sample where n = 1. "
See this extract from my post here on Jan 18th 2014;
"By 1894, Drasche of Vienna was able to cite 27
experiments on themselves by 21 different persons,
of which 10 had been positive in the sense that
varying degrees of diarrhoea had resulted, and 17
had been negative. In most of the positive cases
and a few of the negative, comma bacilli had been
found in the stools."
It is not n = 1, it is at least 27 by 1894. Actually, had just one of these 21 brave subjects died of cholera, I would seriously reconsider my position.
Thank you for referring to me as a loveable old contrarian. I am honoured to be considered in the same breath as Max von P.
"We all know there's a weak experimental science in human infectious disease because it's unethical to knowingly risk a human life."
Fortunately, there is a surprising amount of good experimental data from the 19th century, when doctors were brave and public-spirited, and Ethical Committees had not been invented. Actually, it is surely epidemiological investigations that will sort out cholera transmission. Whilst Snow has contibuted to epidemiology in general, his legacy has blocked cholera studies as people think the question is settled.
"Anthony relies very heavily on extremely old journal articles (which he accesses as hard copies at the library he works in) and appears unwilling or unable to examine more up to date evidence. Perhaps he would like to comment about this?"
The main reason I rely on old articles is that they are available on open access on the shelves as hard copies. My reason for putting up this question on RG was to flush out more modern, though not necessarily more accessible, articles and data. So far, nothing has turned up -- even the Portuguese bottled water study had been well known to me.
Another reason is that these old observations were made by careful observers with open minds as to the water transmission theory (ie pre-Snow), made in times when cholera was a major scourge. If you were an army doctor in India, you probably devoted an inordinate amount of time and energy to thinking about cholera and trying to understand it.
Hi Anthony,
These artices may be of interest...
re unusually heavy rains, algal blooms and cholera outbreaks;
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144830/
re genetic varitaion in vulnerability and water regulation;
http://stm.sciencemag.org/content/5/192/192ra86
.
Paul.
.
Cholera can be transmitted by either contaminated water or contaminated food. In the developed countries, seafood (e.g. oyster) is reported to be the main/usual cause of cholera, whereas in the developing world it is more often water. Oysters grown in sewage contaminated water can accumulate Vibrio cholera in zooplankton (which is the food of oysters). In case of Bangladesh cholera outbreaks are related to plankton blooms and rise of sea temperature.
Both contaminated food and water can transmit cholera. Groundwater or drinking water supplies can harbor the organism.
Yes, it is a very well known fact and unquestionable, historically and in past and even in modern era many public as well as scientifically proven many evidences have confirmed that Cholera is transmitted by contaminated water and food sources, and may lead to huge mortality if not treated timely particularly in infants, childrens and mass gatherings
"this is how cholera can be transferred by drinking water"
"Cholera can be transmitted by...contaminated water"
"Both contaminated food and water can transmit cholera"
"it is a very well known fact and unquestionable, historically and in past and even in modern era many public as well as scientifically proven many evidences have confirmed that Cholera is transmitted by contaminated water"
It is a very well known fact that many people assert that cholera is spread via public drinking water supplies, as Snow believed. Just because it is superficially plausible that it can be spread this way, it does not mean that evidence is not required. It is nearly a year since this question was put up, and still no replication of Snow is forthcoming. Finding vibrios in coastal waters is neither here nor there.
The fact is, it takes 105 V. Cholerae ingestion to have clinical symptoms of cholera and 1 S. dysentery ingestion is enough to have bloody diarrhoea. Now, as both transmits through faeco-oral routes, whatever maybe the medium of transmission.
"it takes 105 V. Cholerae ingestion to have clinical symptoms of cholera"
As pointed out above, there is one epidemic where cholera may have been spread via bottled water. But Snow proposed that it was spread via municipal water supplies. Is it plausible that even if vibrios are present in drinking water, they can ever be in the numbers needed to cause disease, except possibly from a closed bottle?
There is an interesting discussion after Snow's paper in Med Times 1849;20:327. Dr A.P.Stewart observed, that the Commisioners sent to Warsaw in 1832, swallowed cholera evacuations in a concentrated form, yet none died from it. I have not checked this information, but if true, is a conclusive refutation of Snow's water theory, and predates many subsequent failed independent attempts to induce cholera in this way. Stewart also notes that the susceptibility of persons to the disease bears no proportion to their exposure to the disease. Again, a crucial fact, if correct.
Cholera can spread by drinking water if the water is contaminated by vibrio. Please stop this discussion further. It is foolish and wastage of time.
"Cholera can spread by drinking water if the water is contaminated by vibrio. Please stop this discussion further. It is foolish and wastage of time"
Hopefully discussions on RG are settled by evidence, not authority. If Sujit knows of any repliction of Snow's work, then he should cite it here for the benefit of the foolish. Meanwhile, well-meaning agencies are flooding Haiti, bullying the inhabitants about their behaviour and customs. All the more reason for having a large replicable evidence base for their assertions, for sorting the wheat from the chaff.
I have just stumbled upon an interesting series of articles which must cast serious doubt on Snow's overall conclusions based on his investigation of the Soho cholera outbreak. In the absence of any susequent replication of Snow's work, this is a good alternative. King made a detailed house to house survey of two earlier cholera outbreaks in the same area (Med Times 1850;22:138). Of the 134 deaths in 1832, one lived in Broad Street; of 152 deaths in 1849, 5 lived in Broad Street. So clearly the Broad Street pump had nothing to do with these earlier outbreaks.
On the basis of the distibution of cases by street address, King concluded that cholera had a gaseous origin. I do not think his data are consistent with downward spread from the atmosphere above, nor with sideways spread, but localised upward aerial spread from the ground is not excluded.
On p 635, Snow had a long letter criticising an article on chloroform from the previous week's Medical Times, but he did not comment on King's articles.
I hope SN De's cholera exo-toxin evidence is reproduced widely. But, I was told, it takes 106 V. Cholerae ingestion to have clinical symptoms of cholera and in natural system it is improbable to have that high level. So some scientists are probing the mechanism, with specific reference to gut microbiota. So I feel, Anthony G Gordon's question is very valid.
"it is improbable to have that high level."
Would anyone like to hazard a guess as to the maximum level of V.Cholerae that might be found in drinking water? Certain foodstuffs do, however, seem to build up enough concentration of VC on occasion to cause the disease in humans.
>
No, I wouldn't. However I would suggest that would depend heavily on factors such as ambient temperature, whether the water is sourced from a still shallow pool or a large flowing watercourse, etc.
http://www.ncbi.nlm.nih.gov/pubmed/23757128
.
In the Portuguese outbreak of 1974 infection was not just associated with bottled drinking water. Several cases were people who drank directly from spigot/drinking fountains fed from the same spring the bottled water was sourced from. So the environmental circumstances in this incidence obviously allowed a large enough concentration to be achieved in that water source.
Regards,
Paul.
Thanks Paul for the link. Here is the abstract from that article:
Abstract
Cholera, a globally prevalent gastrointestinal disease, remains a persistent problem in many countries including the former Soviet republics of the Caucasus region where sporadic outbreaks occurred recently. Historically, this region has experienced cholera during every pandemic since 1816; however, no known comprehensive evaluation of the presence of Vibrio cholerae in surface waters using molecular methods has been done. Here we present the first report of the presence of V. cholerae in surface waters of Azerbaijan and its seasonality, using a combination of bacteriological and molecular methods. Findings from the present study indicate a peak in the presence of V. cholerae in warmer summer months relative to colder winter months. In the Caspian Sea, water temperature when optimal for growth of V. cholerae was significantly associated with detection of V. cholerae. Vibrio cholerae was simultaneously detected at freshwater sites including two water reservoirs. Most importantly, detection of V. cholerae in these water reservoirs, the source of municipal drinking water, poses a potential health risk to the population due to the limited and insufficient treatment of water in Azerbaijan. Routine monitoring of environmental waters used for recreational purposes, and especially drinking water reservoirs, is highly recommended as a measure for public health safety.
This sounds like a good study with logical and comprehensible findings, but gives no clue as to how VC could have got into spring water, as claimed in the Portugese outbreak. Is VC being spread by water birds? Note the authors do not claim the VC in drinking water poses an actual health risk.
Assuming Snow was right that cholera was spread by drinking water, this can only explain the later cases. It is the explanation for the first case that is crucial. A report on Typhoid Fever and Sewage by George Thompson BMJ 1879;2:795 makes this point:
"Your article...tempts me to place before your readers an account of a series of outbreaks of the same disease which occurred in this asylum during the years 1873-4-5...
"This filthy liquid [water pumped from a steam] was drunk during all the years which lapsed between 1864 and 1873 with apparent impunity, no case of typhoid fever having been recorded ....
The chief interest about this account is not merely that pure sewage may be used with impunity, but that the introduction of the specific 'germ' was followed by first cases as the immediate result, and poisoning of the sewage as a secondary result. This seems, in my mind, to settle conclusively that the importation of a 'first case' is essential to the spread of the disease.."
So, for cholera epidemics, the crucial question is, How did the germ creep round the world from India?
Investigations of cholera outbreaks have clearly demonstrated that drinking water system when contaminated by lickege from sewerage pipe system, drinking water contaminated in this way cause cholera. In some places both the systems run parallel and close enough to seepage water from one system to another.
"Investigations of cholera outbreaks have clearly demonstrated that drinking water system when contaminated by lickege from sewerage pipe system, drinking water contaminated in this way cause cholera. In some places both the systems run parallel and close enough to seepage water from one system to another."
I agree that it has been clearly shown that cross-contamination can and often has occurred. But I cannot find any of the thousands of studies of cholera outbreaks where this has been unambiguously shown to be the vital link. So, could you please cite the one paper that most clearly shows that the cholera was acquired from the drinking water, and preferably finds how it also got into the drinking water in the first place before any case was reported?
"Although our replication effort is novel in its scope and level of transparency – the methods and data for all replicated studies are available online – they are consistent with previous work from other fields. Cancer biologists, for instance, have reported replication rates as low as 11%-25%.
We have a problem. What’s the solution?
Some conclusions seem warranted here.
We must stop treating single studies as unassailable authorities of the truth. Until a discovery has been thoroughly vetted and repeatedly observed, we should treat it with the measure of skepticism that scientific thinking requires. After all, the truly scientific mindset is critical, not credulous. There is a place for breakthrough findings and cutting-edge theories, but there is also merit in the slow, systematic checking and refining of those findings and theories."
(From an article on The Conversation Aug 28, referring to the recent Science article.)
The psychologists are bravely showing the lead here, so will public health epidemiologists follow suit? Or is Snow unassailable?
Here is a recent study which I suspect was an attempted replication of Snow's findings in somewhat similar surroundings. In other words, they were looking to see if cholera was spread via the public water supply. They in fact found the exact opposite -- having access to tap water protected against presumed cholera:
"Cholera risk from unreliable tap water supply
Wednesday, 28 October 2015
Interruptions in continuous piped water supply may lead to an increased number of cholera and other severe diarrhoea cases in urban areas of the Democratic Republic of Congo, according to new research published in PLOS Medicine. The findings from a study conducted in the city of Uvira, on the shores of Lake Tanganyika, suggest cholera control strategies should include providing reliable, continuous tap water supplies in endemic areas. Research led by the London School of Hygiene & Tropical Medicine found a significant association between piped water interruptions, often due to electricity cuts or equipment breakdown, and admissions to a cholera treatment centre in Uvira . Suspected cholera admissions increased by 155% in the 12 days following a day without tap water supply, compared to when supply was at its maximum capacity. The Democratic Republic of Congo has high levels of cholera, reporting 33,661 cases of cholera in 2012, and 819 cholera-related deaths – 27% of global deaths due to the disease. Cholera is an infectious disease that is spread by water or food infected with the bacterium Vibrio cholerae. Supplying clean water is crucial in preventing cholera transmission; however, investing in water supply is expensive, and it is still uncertain what minimum level of access to water is necessary to prevent cholera." From LSHTM website
The UN has apparently acknowledged responsibility for introducing cholera to Haiti. It is alleged that sewage form a UN camp drained into a river, thereby starting an epidemic. If cholera is spread directly via water sources, it follows that cholera should spread down river and not up river. I cannot find any evidence that this was the case in Haiti, and there are plenty of previous epidemics where although cholera spread along water courses it was specifically noted that it spread upstream as much as it did downstream. Epidemics often first used to occur in ports, then spread inland
A summary of Pettenkofer's Memoir on the spread of Cholera in India as translated in Indian Annals of Medical Science appears in London Medical Record 1873;1:14,28,46,61.
P concludes:
"The use of various drinking waters, possibly contaminated with the excreta of cholera-patients, can in no way explain the local and periodical appearance of cholera in India"
The reporter, Corfield, concludes: " After weighing and comparing all the different theories, one comes irresistibly to the conclusion that there is some essential factor in the cholera process that has yet to be dragged to the light.."
Comment
Why would Pettenkofer, a meticulous observer, dismiss Snow's theory given that P was greatly concerned about preventing cholera epidemics in Europe? Clues to the transmission of cholera must surely come from close examination of the old epidemiological data from India, where it was a major problem for the British Army, rather than from superficial observations from Haiti today replete with confirmation bias.
"Japanese troops also dropped cholera and typhoid cultures in wells and ponds, but the results were often counterproductive. In 1942 germ warfare specialists distributed dysentery, cholera and typhoid in Zhejiang Province in China, but Japanese soldiers became ill and 1,700 died of the diseases, scholars say.Sheldon H. Harris, a historian at California State University in Northridge, estimates that more than 200,000 Chinese were killed in germ warfare field experiments. Professor Harris -- author of a book on Unit 731, "Factories of Death" (Routledge, 1994) -- also says plague-infected animals were released as the war was ending and caused outbreaks of the plague that killed at least 30,000 people in the Harbin area from 1946 through 1948.
The leading scholar of Unit 731 in Japan, Keiichi Tsuneishi, is skeptical of such numbers. Professor Tsuneishi, who has led the efforts in Japan to uncover atrocities by Unit 731, says that the attack on Ningbo killed about 100 people and that there is no evidence of huge outbreaks of disease set off by field trials."
Kristof ND New York Times 1995 Mar 17
***********************************************************************
After spending some time on the Internet, my overall conclusion of what should have been a definitive test of Snow's hypothesis, was that deliberate cholera infection of the water supply was probably ineffective. But does anyone know of more definitive data from what was a unique circumstance, preferably before some terrorists try it again now?
"Yemen has been ravaged by hunger and civil war, allowing disease to spread rapidly.
Two-thirds of the population do not have access to safe drinking water, according to the UN...
Image copyright Reuters Image caption Lack of clean drinking water is exacerbating the problem
Sanaa has been worst hit, followed by the surrounding province of Amanat al-Semah, the World Health Organisation (WHO) says.
Cholera is a water-borne disease that is transmitted through contaminated water and food." BBC News May 17, 2017
Comment
Nearly 4 years after my original question and still the dogma that cholera is a water-borne disease is uncritically trotted out. Even if it were, then, as seen above, it does not seem to be transmitted by the municipal water supply, as alleged by Snow.
Given that Snow's work was so inconclusive, where does this leave the waterborne theory? Koch (Int J Epidem 2013;42:1553, see extract below) does not say what is left if Snow is discounted:
"The myth of Snow's brilliance is thus transformed from a hero story into a cautionary tale. Snow had a good idea. Indeed, he had a great idea. Cholera is waterborne, after all. But in presenting this idea, and a disease theory tied to it, he failed to employ the best methodologies of the day...
I argued the falsity of the claims made on Snow's behalf by modern historians. Snow did not create 'show leather' epidemiology or mapped cartography. He did not create the experimenta cruces. He did not prove cholera was waterborne"...
...so who was it that did?
I have tried and failed several times to register as I'm not involved with research work. I had wanted to add the following...perhaps you could post it on my behalf?
Response from Ann-Marie Cousins: [email protected]
"My personal experience is that on the morning of Monday the 3rd July 2017 I started the obvious vomiting and diarrhea of food poisoning symptoms. I was in Lagos, Sasha State, having arrived there from London the evening of Wednesday 28 June. I started to feel physically unwell on Sunday 2nd July. Leading up to that I was feeling very tired from lack of a good nights sleep, noisy generators and several people sharing a room / house.
I am not 100% certain how I contracted Cholera. I self diagnosed what it was via the internet when I returned to London - the classic 'rice water' discharge being key. A sample sent for analysis by my Dr came back negative. It was tested for likely UK bacteria e.g. e-coli & salmonella but not Cholera - even though my Dr noted on the request form that I had returned from Nigeria!!
In Sasha State, Lagos, I did not eat a lot. Two days later I bought from the open market (alongside open sewers), the green leafy veg Ugu, washed it and soaked it in salted water for about 20 minutes before eating some leaves uncooked with cooked rice. The rest was eaten cooked with yam the following day. On return to London, I again learnt via the internet that Cholera is tolerant of salty water.
In Sasha, I drank only bottled water, but I did shower and brush my teeth using their tap / pumped water. So it is possible that I caught Cholera via washed raw Ugu, dust, water used for washing and from mouth / breath contamination due to the proximity of so many people in one facility and the pouring of some of my bottled water into one specific individual's mouths without lips touching the bottle's opening.
Back in London, 6 days later (12 July), when I started to feel better, without thinking my daughter took a bit from something I had just bitten. A few hours later she started vomiting & diarrhea. It is not possible that my daughter caught it from feacal transmission as my diarrhea had abated by then, she had bitten the food item directly after me and I have my own en-suite bathroom and so the potential for cross-contamination is limited.
It seems to me, based on my personal experiences that I potentially contracted Cholera via water. The shared bottle without direct contact could potentially be the route as that incident occurred earlier in the day on the Sunday - the evening of which I started to feel unwell but was putting it down to tiredness. So was there breath or splash back contamination of my bottled water? Being tired and nutritionally depleted possibly made me more vulnerable. And, without room for dispute, my daughter caught it directly from biting into an apple pie, directly over where I had just bitten. Fortunately for her, after a terrible 24 hour period she made a rapid recovery and did not progress to the 'rice water' feacal discharge stage.
I have concluded from this personal experience that Cholera is highly contagious and that mouth to mouth, bitten foods and even water droplets via breath are routes of transmission that has to be further investigated. The younger and healthier you are along with rapid re-hydration, the better the prognosis."
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