STEALTHY VIRUS: From recent reports about the stealthy ways the so-called Covid-19 virus spreads and maims, a picture is emerging of an enigmatic pathogen whose effects are mainly mild, but which occasionally — and unpredictably — turns deadly in the second week. In less than three months, it's infected about 77,000 people, mostly in China, and killed more than 2,200.
US National Institute of Allergy and Infectious Diseases