https://www.medrxiv.org/content/10.1101/2020.09.16.20194787v1
As much as two-thirds of the population of Manaus, a city of two million people in Brazil’s state of Amazonas, could have been infected with the new coronavirus. That’s a proportion high enough to have contributed to controlling the spread of the virus.
Ester Sabino at the University of São Paulo, Brazil, and her colleagues searched for antibodies against SARS-CoV-2 in more than 6,000 blood samples collected by a Manaus blood bank between February and August (L. F. Buss et al. Preprint at medRxiv https://doi.org/ghcm6h; 2020)---as above . From the proportion of donors who tested positive for antibodies, the authors estimate that about 66% of the population had been infected by early August — months after the epidemic in Manaus peaked in May . A queer way of developing herd immunity!!
Coronavirus Cases:
32.5 million
Deaths:
988 k
Recovered:
24 million
So my understanding is this is actually a positive outcome?
An individual's immunity can be acquired via natural infection or through vaccination and individuals who are immune to a disease act as a barrier in the spread of disease. When a critical proportion of the population becomes immune, called the herd immunity threshold (HIT), the disease may no longer persist in the population.
Herd immunity threshold (HIT) for COVID-19 is 60-70%, if the infected population exceeds it, the number of cases reduces at a faster rate, outbreaks are likely to end.
https://en.wikipedia.org/wiki/Herd_immunity
The unrelenting surges of SARS-CoV-2 in Brazil may be indicative of three possibilities 1. The rapid waning of the SARS-CoV-2 antibodies may never make the herd immunity a reality in the long-term 2. Reinfections in previously recovered SARS-CoV-2 patients may be occurring 3. Just like the case of another RNA virus, Hepatitis C, where anti-HCV antibodies do not indicate immunity, the same may be the implications of antibodies to SARS-CoV-2.
These hypothesis would be clarified better whether a COVID-19 vaccine becomes a reality and also decreases SARS-CoV-2 infection or reinfection rate in vaccinated patients.
Do you think that infection generates immunity in those infected with the virus?
Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune.
Often, a percentage of the population must be capable of getting a disease in order for it to spread. This is called a threshold proportion. If the proportion of the population that is immune to the disease is greater than this threshold, the spread of the disease will decline. This is known as the herd immunity threshold.
What percentage of a community needs to be immune in order to achieve herd immunity? It varies from disease to disease. The more contagious a disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread. For example, the measles is a highly contagious illness. It's estimated that 94% of the population must be immune to interrupt the chain of transmission.
https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/herd-immunity-and-coronavirus/art-20486808
Herd immunity can also be reached when a sufficient number of people in the population have recovered from a disease and have developed antibodies against future infection. For example, those who survived the 1918 flu (influenza) pandemic were later immune to infection with the H1N1 flu, a subtype of influenza A. During the 2009-10 flu season, H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu.
However, there are some major problems with relying on community infection to create herd immunity to the virus that causes COVID-19. First, it isn't yet clear if infection with the COVID-19 virus makes a person immune to future infection.
Research suggests that after infection with some coronaviruses, reinfection with the same virus — though usually mild and only happening in a fraction of people — is possible after a period of months or years. Further research is needed to determine the protective effect of antibodies to the virus in those who have been infected.
https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/herd-immunity-and-coronavirus/art-20486808
Even if infection with the COVID-19 virus creates long-lasting immunity, a large number of people would have to become infected to reach the herd immunity threshold. Experts estimate that in the U.S., 70% of the population — more than 200 million people — would have to recover from COVID-19 to halt the epidemic. If many people become sick with COVID-19 at once, the health care system could quickly become overwhelmed. This amount of infection could also lead to serious complications and millions of deaths, especially among older people and those who have chronic conditions
https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/herd-immunity-and-coronavirus/art-20486808
Massive Covid-19 infection within a given population can lead to herd immunity, however, some lives would have been lost in the process
An update for Emergency Clinicians :
https://www.ebmedicine.net/topics/infectious-disease/COVID-19
the latest on herd immunity:
https://www.sciencenews.org/article/coronavirus-covid-19-brazil-city-manaus-herd-immunity
Anthony Fauci repels herd immunity:
https://www.medscape.com/viewarticle/937992
Herd immunity can be achieved through extremely high infection rate
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