Epidemiological characteristics of clusters of COVID-19 in Anhui province

  Objective  To examine epidemiological characteristics of cluster epidemic of novel coronavirus disease 2019 (COVID-19) in Anhui province for providing evidences to prevention and control of the epidemic.

  Methods  The data on confirmed COVID-19 cases reported from January 1st to February 23rd, 2020 in Anhui province were extracted from Information System for Disease Prevention and Control sponsored by China Center for Disease Control and Prevention. Descriptive statistics was conducted to analyze the clustering of the reported cases.

  Results  During the period from January 23 to February 23, 2020, a total of 176 clusters of COVID-19 were identified in the province, involving 564 cases reported and 90.9% of the cluster incidences occurred in family settings. For all the reported cases, 497 were confirmed cases, accounting for 50.3% (497/989) of the total confirmed cases during the period in the province; among the confirmed cases, 67 were positive for 2019 novel coronavirus (2019-nCov) nucleic acid, accounting for 52.8% (67/127) of all positive cases during the period. A peak from 3 – 11 February was observed for the clustering incidence occurred in all 16 prefectures across the province and 48.9% (86/146) of the cluster cases were reported in northern regions of the province. The proportion of the transmission source varied over time; the ratio of the first cases of the clustering incidents with the history of travelling experience in Wuhan city decreased from 81.8% to 18.9% but that of the first case with the history of contacting with local suspected infections increased from 0 to 40.5%. Of all the clustering incidents, 53.4% were probably due to exposures of living together and having dinner together with relatives.

  Conclusion  The clustering of novel coronavirus disease 2019 were mainly familial clusters in Anhui province and about a half of the clusters occurred in northern regions of the province. The exposure history of the first cases of the clusters changed from in Wuhan city initially to local regions subsequently. Living together and having dinner party with relatives or friends are probably the main ways of infection transmission.