[lazide]

That seems unlikely, if for no other reason than the way COVID has spread. Do you have any data?

All the data I've seen on SARs and the mechanisms deployed to control it indicate infectivity at or only very, very shortly before clear symptoms or they would not have been able to control it.

COVID is quite clearly infectious before visible symptoms of any kind, and even when visible many times symptoms are pretty mild - where SARs was not - and this matches it's observed spread and difficulty in controlling it.