R0 represents the average number of susceptible individuals an infected person will transmit the disease to.
R0 = Attack rate x Contacts
Attack rate (the percent chance that a contact will get the disease).
If the R0 is < 1, a disease outbreak should wane over time, and if its >1, cases would continue to increase.
Seasonal flu has an R0 of around 1.5. The Spanish influenza of 1918-1919 had an R0 of 2. Chickenpox, a fairly infectious condition, has an R0 of around 5.
To predict the severity of a new disease, we need to look at both the basic reproduction number and the case fatality rate.
The case fatality rate of Spanish flu was reported to be as high as 10%.
Before treatment was available, HIV, with an R0 of around 6 globally, had a near 100% mortality rate. Smallpox, with an R0 of 5, had a mortality rate of 30% in the unvaccinated. Bubonic plague: R0 of 3, untreated mortality rate of 60%.
COVID-19
COVID-19 has R0 of 2.5 and a reported case fatality rate of around 2%.
Case fatality rate is defined as the number of fatal cases divided by the number of total cases.
In COVID-19, fatal cases have probably been assessed accurately; people who are that sick generally end up in hospitals. However, the number of total cases are probably being missed by huge margins, perhaps even an order of magnitude, as asymptomatic and mildly symptomatic people may not be getting tested. If this is the case, the case fatality rate would decrease as screening improves.
How to change the R0 number
One can do that by addressing the two elements inside it: the number of contacts an infected person has and the attack rate of the disease.
Limiting potential contacts can be achieved by means of isolation and quarantine.
Attack rate can reduce with the use of masks, handwashing, and vaccination, as and when a vaccine becomes available.
This depends on identifying cases, and it is still unclear as to whether transmission can occur in the asymptomatic period. The latent period is 5 days.
Please check:
https://www.ijidonline.com/article/S1201-9712(20)30091-6/fulltext
hi dear
https://www.ijidonline.com/article/S1201-9712(20)30091-6/fulltext
But it was on an almost closed environment that is on a cruise ship where the people will be almost forced to interact with each other. So can we extrapolate the findings to the general population. Will that not be a boss.
The attack rate or transmissibility of a virus is indicated by its reproductive number (Ro, pronounced R-nought or r-zero), which represents the average number of people to which a single infected person will transmit the virus.
WHOs estimated (on Jan. 23) Ro to be between 1.4 and 2.5.
Other studies have estimated a Ro between 3.6 -4.0, and between 2.24- 3.58.
Preliminary studies had estimated Ro to be between 5 and 3.5.
An outbreak with a reproductive number of below 1 will gradually disappear.
For comparison, the Ro for the common flu is 1.3 and for SARS it was 2.0.
So, with this one person can only infect 3-34 people.
However, it is a well-known fact that HIV with Gonorrhoea combination spreads HIV more rapidly than a person with HIV alone. A ‘super spreader’ is a fast spreader.
A South Korean patient has been linked to spreading the coronavirus to over 1,000 people and is a perfect example which goes ahead to show the significance of social distancing. The Asian country saw an increase in cases from hundreds of cases to thousands within days with a super spreader labelled "patient 31" linked to 1,160 cases. In the days before the diagnosis was confirmed, the woman who was a member of a large cult called Shincheonji, had multiple contacts with large gatherings.
Keeping in view social lockdown seems a logical step followed by many countries.
God bless us all.
It has been observed that even a totally asymptomatic COVID 19 positive patient has the ability to spread the infection to his close contacts. They can get infected from a symptomatic individual and remain without any symptoms and still infect others, but proper use of masks and maintaining social distance can reduce the number of persons they infect.