Asymptomatic Subclinical Cases of Coronavirus Disease 2019 without Viral Transmission in Three Independent Families

PURPOSE: There is increasing evidence indicating that considerable fractions of cases of SARS-CoV-2 infection are asymptomatic. We traced three asymptomatic clusters to investigate the infectivity of subclinical cases of coronavirus disease 2019 (COVID-19). PATIENTS AND METHODS: Three medical staff who were asymptomatic were diagnosed with coronavirus disease 2019 by serological tests. Their close contacts were systematically evaluated based on COVID-19-related symptoms, nucleic acid tests, serological tests, and chest computed tomography (CT) as needed to determine if they were infected by SARS-CoV-2. RESULTS: None of the staff's close contacts, including 10 family members, were infected by the indexes, even though no protective measures were taken. CONCLUSION: The infectivity of asymptomatic subclinical infection patients of coronavirus disease 2019 seems to be low.