system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it that coronavirus has defined "peaks" when spreading throughout a community?

I was just reading a forecast for my states omicron case projected "peak time", which is something like 10 days where the cases will peak (and then trough/plateau?). I am confused to the reasoning or rationale behind this projection, is it because people will become sick, then subsequently will have to isolate and/or people who have already been sick during the peak maintain a natural immunity so it can't keep spreading like wildfire to the \*almost\* entire population? 

Please help, I hope this post makes sense!
gpt
You pretty much already understand it. It’s a general concept of exponential growth. Spread occurs exponentially with a speed dictated by how infectious the virus is (the R value) to susceptible individuals. At a certain point, the number of new people that would need to be infected for the exponential growth to continue will be larger than the number of vulnerable people and exponential growth must stop. In practice, exponential growth in biological systems levels off well before that point, because there’s a limiting resource that prevents it from occurring. In the case of a virus, people that are sick interact with less people and more people become immune after having the virus giving the virus fewer new people to infect and levelling off the curve. The same applies to the growth of bacteria in laboratory medium. At some point, there’s going to be more biomass than the remaining nutrients can support and growth will level off and decline.