– 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
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.
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