Abstract：Objective To investigate a cluster of coronavirus disease 2019(COVID-19)caused by latent infection in Haikou,so as to provide reference for the prevention and control of COVID-19 clusters. Methods An epidemiological investigation was conducted according to the COVID-19 Prevention and Control Program(Fourth Edition). The course of diagnosis and treatment,clinical characteristics and field investigation data were collected to analyze the transmission chain and the intergeneration between cases. Results Among 39 people involved,five confirmed cases and two asymptomatic infections were found,with an attack rate of 17.95%. The cases aged from 40 to 65 years and lived in the dormitories near the farm of Dongshan. The first case(named Case 1)closely contacted with a confirmed case of COVID-19 in Chengmai from January 28 to February 10,was isolated on February 13 and developed symptoms on February 16. The other six cases(Case 2 to Case 7)shared the water source with Case 1 from January 28 to February 13(within the incubation period of Case 1). They needed to open the power switch outside Case 1's room and the water valve in Case 1's washroom before the use of water. They might be infected by contacting the doorknob and the water valve contacted by Case 1,or by the aerosol formed after Case 1 used the washroom,then infected each other when living together. The onset of Case 2 to Case 7 was earlier than Case 1,and they had no travelling history in Hubei Province 14 days before and contacted no confirmed cases except Case 1. Therefore,Case 1 was the source of the cluster during his incubation period of COVID-19. Conclusion This was a cluster of COVID-19 due to latent transmission by living in the same area and touching the same objects indirectly,which indicated that COVID-19 was infectious in the incubation period.
 中华人民共和国国家卫生健康委办公厅,中华人民共和国国家中医药管理局办公室.关于印发新型冠状病毒肺炎诊疗方案(试行第七版)的通知[EB/OL].(2020-03-04)[2020-04-06].http://www.nhc.gov.n/yzygj/s7653p/202003/46c9294a7dfe4cef80dc7f5912eb1989.shtml.  中华预防医学会新型冠状病毒肺炎防控专家组.新型冠状病毒肺炎流行病学特征的最新认识[J].中华流行病学杂志,2020,41(2):139-144.  中华人民共和国国家卫生健康委员会办公厅.关于印发新型冠状病毒肺炎防控方案(第四版)的通知[EB/OL].(2020-02-07)[2020-04-06].http://www.nhc.gov.cn/jkj/s3577/.  202002/573340613ab243b3a7f61df260551dd4.shtml.  中国疾病预防控制中心.关于印发新型冠状病毒肺炎病例密切接触者调查与管理指南(试行版)的通知[EB/OL].(2020-02-24)[2020-04-06].http://www.chinacdc.n/acdc.n/jkzt/crb/zl/szkb_11803/jszl_11815/202002/t20200224_213676.html.  中华人民共和国国家卫生健康委办公厅,中华人民共和国国家中医药管理局办公室.关于印发新型冠状病毒肺炎诊疗方案(试行第五版修正版)的通知[EB/OL].(2020-02-08)[2020-04-06].http://www.nhc.gov.cn/yzygj/s7653p/202002/d4b895337e19445f8d728fcaf1e3e13a.shtml.  中国疾病预防控制中心新型冠状病毒肺炎疫情防控流行病学组和防控技术组.新型冠状病毒肺炎聚集性疫情流行病学调查技术指南(试行第一版)[J].中华流行病学杂志,2020,41(3):293-295.  GUAN W J,NI Z Y, HU Y, et al. Clinical characteristics of coronavirus disease2019 in China[J].N Engl J Med,2020(2020-02-28)[2020-04-06].https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7092819/.  WANG P,LIAN Z Y,CHEN Y,et al.Investigation of a cluster of 2019 novel coronavirus disease (COVID-19) with possible transmission during the incubation period—Shenyang city, China,2020[J].China CDC Weekly,2020,2(8):125-127.  YU P,ZHU J,ZHANG Z,et al. A familial cluster of infection associated with the2019 novel coronavirus indicating potential person-to-person transmission during the incubation period[J].J Infect Dis,2020(2020-02-18)[2020-04-06].https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7107453/.