[confeit]

> Human intervention may have placed more severe selective pressure on the L type, which might be more aggressive and spread more quickly.

Harder to detect I would see in a strain that has a longer asymptomatic spread period. The only way for a virus to escape a strong quarantine and survive is to survive on surfaces longer, be asymptomatic longer, cause more severe illness (spread through cough and sneezes, especially in hospitals), linger in the air longer, etc.

[riffraff]

> cause more severe illness

on the contrary, more sever illness makes it less likely to spread, no?

You are always spreading germs around, if you have high fever or start coughing blood you'll get isolated but if you just have a runny nose you will keep living normally and the virus will happily keep infecting other people when you shake hands.

[confeit]

During quarantines people are not shaking hands. I am not saying quarantines necessarily select for a higher death rate (a dead host can not spread), but for a more severe disease (the main drivers of a spread are when people ultimately develop severe symptoms).

Community viruses mutate to see a lower mortality, severity, and infectiousness, since there is no selective pressure to have an r0 much higher than 1. For a community virus there is also no selective pressure to mutate to a vastly different strain, so the antibodies for other strains don't help, whereas if the virus is confined inside a city like Wuhan, the only way to reinfect is to mutate to a vastly different strain.