Incubation periods of 156 COVID-19 cases with exact exposure time in Hunan Province
ZHAO Shan-lu, LUO Kai-wei, HUANG Yi-wei, HU Shi-xiong, LI Fang-cai, XIAO Jie-hua, ZENG Ge, ZHANG Heng-jiao, YANG Hao, SUN Qian-lai, DAI Zhi-hui, LIU Zi-yan, CHEN Sheng-bao, GAO Li-dong
Hunan Provincial Center for Disease Control and Prevention/Hunan Workstationfor Emerging Infectious Disease Control and Prevention, Chinese Academy of Medical Sciences, Changsha, Hunan 410005, China Author contributions: ZHAO Shan-lu and LUO Kai-wei contributed equally to this paper
Abstract：Objective To analyze the incubation periods of 156 COVID-19 cluster cases with exact exposure time, and to provide a basis for COVID-19 prevention and control strategies and measures. Methods Data concerning COVID-19 cluster cases reported in Hunan Province from January to February 2020 were collected. According to the cases' exposure and onset time, the incubation periods of the COVID-19 cases were estimated by median method. Differences in the incubation periods of different exposure modes were compared by rank-sum test, and the information about 3 cases with extra-long incubation periods was described. Results The average incubation period for 156 confirmed cases with exact exposure time was 7.0 days, and theinterquartile interval Q was 5.0 days. The average incubation period for 53 cases with single source exposure was 6.0 days, with the interquartile interval Q being 5.0 days. The average incubation period for 103 cases with multiple exposure was 7.5 days, with the interquartile interval Q being 5.0 days. The incubation period (5.0 days) of sharing a same car and close talk exposure was shorter than that of dinner exposure (8.0 days) (Z=-2.589,P=0.01). The shortest incubation period of family exposure (2.0 days) was shorter than that of non-family exposure (5.5 days) (Z=-3.335, P=0.001). The incubation periods of 3 cases exceeded 14 days, which were 16, 16 and 17 days, respectively. Conclusion The average incubation period for the COVID-19 cases was 7.0 days. The risk of COVID-19 transmission due to family exposure was higher, and there were cases with extra-long incubation period. Early detection and isolation of the cases and close contacts are important means to prevent further spread of the epidemic.
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