Introduction:Since emerging in Wuhan, China, in December 2019, the coronavirus disease 2019 (COVID-19) epidemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has progressed rapidly into a pandemic [1].COVID-19 is characterized by fever, cough, fatigue, shortness of breath, pneumonia, and other respiratory tract symptoms,[2–4] and in many cases progresses to death. As of April 15, 2020, there have been 1914916 confirmed cases and 123010 deaths reported worldwide.5 Most cases were initially confined to Hubei province in China, but there has since been substantial spread not only elsewhere in China but worldwide. A rapid and robust response by the global scientific community has described many important aspects of SARS-CoV-2 transmission and natural history,[6–8] but key questions remain.