Athena Aktipis and I wrote a piece about this in TheConversation.com:
Here is an excerpt:
Viruses walk a fine line between severity and transmissibility. If they are too virulent, they kill or incapacitate their hosts; this limits their ability to infect new hosts. Conversely, viruses that cause little harm may not be generating enough copies of themselves to be infectious.
But SARS-CoV-2, the coronavirus that causes the COVID-19 disease, sidesteps this evolutionary trade-off. Symptoms often don’t appear until after infected people have been spreading the virus for several days. One study of SARS-CoV-2 estimated that the highest rate of viral shedding, and therefore transmissibility, was one to two days before the person infected begins to show symptoms.
Put simply, you only feel ill once the virus has accomplished its evolutionary goal: to spread.
Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine