The first pneumonia case of unknown cause was found close to a seafood market in Wuhan, the capital city of Hubei province, China, on December 8, 2019. Several clusters of patients with similar pneumonia were reported through late December 2019. The pneumonia was later identified to be caused by a new coronavirus (severe acute respiratory syndrome coronavirus 2, or SARS-CoV-2) (Zhu et al. 2020), later named Coronavirus Disease 2019 (COVID-19) by the World Health Organization (WHO).1 While the seafood market was closed on January 1, 2020, a massive outflow of travelers during the Chinese Spring Festival travel rush (Chunyun) in mid-January2 led to the rapid spread of COVID-19 throughout China and to other countries. The first confirmed case outside Wuhan in China was reported in Shenzhen on January 19 (Li et al. 2020). As of April 5, over 1.2 million confirmed cases were reported in at least 200 countries or territories.3