> only useful if YOU have the virus Yes, but given the incubation period and so on, how do you know you don't have the virus? I'm not going to wear a mask in

> only useful if YOU have the virus Yes, but given the incubation period and so on, how do you know you don't have the virus? I'm not going to wear a mask in Central Europe (at least not yet) but I probably would in Asia just in order to not be selfish.