Objective  To analyze a family clustering of coronavirus disease 2019 (COVID-19) associated with the exposure to an asymptomatic case and to provide evidences for developing strategies for COVID-19 prevention.

  Methods  We conducted a field survey on a cluster epidemic of COVID-19 occurred between January 31 to February 6, 2020 in Chenzhou city of Hunan province. Throat swab specimens of the cases were detected for novel coronavirus nucleic acid with real-time fluorescence quantitative polymerase chain reaction.

  Results  The clustering epidemic occurred within 6 days in a family, involving 4 confirmed cases and one asymptomatic case. The first case of the clustering was 56-year old man laboratory confirmed 6 days after the onset of symptoms and the case reported no history of traveling in or contact with someone from the epidemic region. The second case was the first case′s son (30 years old) without clinical symptoms but positive for novel coronavirus nucleic acid one day after the diagnosis of the first case; the third case was the son′s wife, a confirmed case based on viral nucleic acid positive and lung X-ray examination but without clinical symptoms; the couple had long-term history of living and working in Wuhan city and went to their father′s home during Spring Festival holiday. Other two cases of the clustering were the son′s mother (52 years) and daughter (2.5 years), who had no no history of traveling in or contact with someone from the epidemic region. The family members lived together in the first case′s home and did not report taking measures to prevent the disease. The family COVID-19 clustering was probably induced by exposure to the couple having no physical symptoms of the disease based on the information collected.

  Conclusion  The family COVID-19 clustering may be induced by the exposure to an asymptomatic case, suggesting that identification of asymptomatic cases is very important for the control of COVID-19 epidemic.