Do Masks Work? What We Know About Coronavirus Transmission

Officials of the World Health Organization say it’s now clear how the new coronavirus that causes Covid-19 spreads, at least in most cases. It’s transmitted via virus-containing droplets emitted when an infected person coughs or sneezes. Other possible routes of contagion are still under investigation. Doctors in China have explored, and seemingly discarded, the possibility the virus could be passed in utero after the infection appeared in babies born to mothers with the disease. Pinpointing whe