[Epidemiological characteristics of COVID-19 family clustering in Zhejiang Province]

Objective: To investigate the epidemiological characteristics for family clusters of COVID-19 in Zhejiang Province. Methods: The data including cases information of asymptomatic infected cases of family clusters of COVID-19 in Zhejiang Province were collected from Public Health Emergencies Reporting System of China Center for Disease Control and Prevention. Calculate the case number of subsequent cases, index cases, asymptomatic infected cases, exposure cases, and then, compute family secondary attack rate (SIR) and serial interval. Results: A total of 389 cases comprised 149 family index cases and 240 subsequent cases. The clinical symptoms between family index cases and subsequent cases (exclude asymptomatic infected cases ) were similar, fever was the most common symptoms in the two groups 115 (77.18%) and 110（48.67%）respectively, the cases with diarrhea symptoms accounted for the least proportion, which were 7 (4.70%) and 6 (2.65%) respectively. The serial interval between the family index cases and the subsequent cases [M (P₂₅, P₇₅)] was 4.00 (2.00, 6.00) days. Family secondary attack rate for subsequent cases was 34.43%, subsequent cases aged between 14 and 60 have the highest SIR (43.42%) compared with other two age groups, the difference was statistically (P<0.001); the family SIR of the spouses of the family index cases is 68.57%, and are higher than that of parents (29.03%), children (25.00%) and other family members (24.21%), the difference was also statistically (P<0.001). Conclusion: 2019 novel coronavirus has shorter serial interval and higher family SIR, the SIR of spouses is higher than other family members.