As the number of cases of infection with the novel coronavirus (SARS-CoV-2) has continued to increase, many countries have established restrictions regarding travelers who have recently visited China.1 With lockdown measures imposed in Hubei Province, China,2 and a public health emergency of international concern declared by the World Health Organization,3 foreign nationals have sought to return to their home countries from China, and public health authorities are racing to contain the spread of Covid-19 (the disease caused by SARS-CoV-2 infection) around the world. This process is complicated by epidemiologic uncertainty regarding possible transmission of the virus by asymptomatically or subclinically symptomatic infected persons. It is unclear whether persons who show no signs or symptoms of respiratory infection shed SARS-CoV-2.

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