# – The infестion R-naught. If a positive-tested person is locked in a room with 20 other people for 1 week, touching their faces, hugging and talking to all, will all of them get infected?

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– The infестion R-naught. If a positive-tested person is locked in a room with 20 other people for 1 week, touching their faces, hugging and talking to all, will all of them get infected?

In: Biology

Depends on the method of transmission. If you locked yourself in a room with an HIV positive person and did all that, your chances are pretty low unless you decide to swap body fluids.

Do the same with a flu patient and one sneeze or cough could do it

Which infectious agent are you talking about. If it’s Sars-Cov-2, they wouldn’t have to hug or touch at all. In an enclosed room the infected individuals breathing alone would be enough to aerosolize and circulate viral particles. There have been a number of studies of localized outbreaks where people were infected just by sitting in the same office for long enough even though they were 60+ feet away.

Possibly, but that has little to do with the R_0 quantity in populaтion modelling. The R_0 indicates the average number of individuals a single individual will infect over the course of its life (or equivalently, whatever time they are contagious).

If you have one person infected and you’re only considering one week, the R_0 is not a very useful metric.

R0 (very roughly) describes the rate at which a disease will spread through a population given a variety of assumptions. It is not, as is commonly represented, some absolute property of a disease.

Consider HIV. Amongst a community of gay men, HIV has a relatively high R0. While it is difficult to transmit, the length of time someone remains contagious is enormous – you can live a decade or more HIV positive without any treatment. Amongst a community of European heterosexuals, HIV has an R0 so low that it might as well be zero.

Viruses like influenza or COVID-19 are a bit more egalitarian. They can be carried along with the water droplets you exhale (and breath in). However, they also tend to kill their victims quickly, giving the virus a limited time to spread.

However, all viruses are not – as is commonly stated – exponential in growth. Rather they are *network effects*. Think of a social media site like Twitter. Some people have millions of followers. Some people only have a few. If a Kardashian posts a message, that information will spread rapidly. If my Uncle Mel posts a message, it won’t.

Physical contacts with human beings work much the way, albeit on a smaller scale.

What you are positing is a situation rarely encountered in human society: one where everyone is a ‘high traffic node’. Every person in your locked room has roughly similar levels of (frequent) contact with every other person in that room. So *any* disease that can be transmitted by such measures *will* be transmitted across your entire population (of the locked room) with an extraordinarily high R0.

The same disease introduced into an actual human society would have a much lower R0.