In December 2019, a cluster of patients with pneumonia of unknown cause was reported in Wuhan, China (1). The causative pathogen was subsequently identified as severe acute respiratory syndrome–related coronavirus-2 (SARS–CoV-2) (2), a newly described betacoronavirus. This virus, now recognized as the etiologic agent of COVID-19 disease, is the seventh known coronavirus to infect humans (1). Since the recognition of COVID-19, there has been an exponential rise in the number of cases worldwide. As of 1 April 2020, the World Health Organization reported more than 926 000 cases in more than 195 countries, areas, or territories (3). Reasons for the rapid spread include high transmissibility of the virus (4, 5), especially among asymptomatic or minimally symptomatic carriers (6, 7); the apparent absence of any cross-protective immunity from related viral infections; and delayed public health response measures (8–10).