[Myrddin]

Before we had truly "mass" transportation, a deadly virus like Ebola would "burn out" as it killed people in a walking radius of the kill time. A 2 day radius. Once burned out, it ceased spreading. It occurred only in low population density areas e.g. Africa. The whole equation changes if you put Ebola in a New York subway.

Successful viruses spread asymptomatically and delay their pathogenic effects long enough to propagate to a wider audience. HIV is a good example. SARS-CoV-2 is successful to the extent that is spreads easily before the pathogenic effects present. It kills relatively slowly compared to Ebola. Immunity on recovery lasts about 90 days and the mutation speed is rapid enough to see recovered individuals infected with a new mutation.

[ifinnegan]

You like to make crap up, I see.

[null and void]

The whole equation changes if you put Ebola in a New York subway.

To be fair, Ebola nurse Kaci Hickox rode a bike to the pizzeria when she was theoretically in quarantine.

She didn't take the subway...