Commuters wear face masks as a precaution against the COVID-19 illness inside a subway station during rush hour in Hong Kong, Wednesday, March 11, 2020. For most, the coronavirus causes only mild or moderate symptoms, such as fever and cough. But for a few, especially older adults and people with existing health problems, it can cause more severe illnesses, including pneumonia. (AP Photo/Kin Cheung)

March 11, 2020