Viruses are interesting things. I once enjoyed a case study about an outbreak of common cold on an Antarctic base that only happened after 17 weeks of isolation: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2130424/
(I'm no virologist but given that the common cold didn't seem to be impacted by the severe lockdowns in the UK at all, whereas flu was, I've gotten the - uneducated - feeling the cold is a bit like some STDs in the way it can linger around in people and pop up whenever the conditions are right. Maybe some COVID variant will end up similarly persistent and endemic?)
(I'm no virologist but given that the common cold didn't seem to be impacted by the severe lockdowns in the UK at all, whereas flu was, I've gotten the - uneducated - feeling the cold is a bit like some STDs in the way it can linger around in people and pop up whenever the conditions are right. Maybe some COVID variant will end up similarly persistent and endemic?)