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.