The most insidious thing about the COVID-19 coronavirus is that people can be infected and highly contagious while showing no symptoms. If everyone who got it suffered obvious symptoms before being contagious, as was the case with SARS, it would be easy to isolate the sick and stop the spread of the disease. Since that is not the case, there constantly is the chance that an asymptomatic or presymptomatic person can unknowingly infect others and why social distancing and masks are so necessary...