Detailed virological analysis of nine cases of coronavirus disease 2019 (COVID-19) provides proof of active replication of the SARS-CoV-2 virus in tissues of the upper respiratory tract.
Coronavirus disease 2019 (COVID-19) is an acute infection of the respiratory tract that emerged in late 2019(1,2). Initial outbreaks in China involved 13.8% of cases with severe courses, and 6.1% of cases with critical courses(3). This severe presentation may result from the virus using a virus receptor that is expressed predominantly in the lung(2,4)
