Abstract：Objective To analyze the epidemiological characteristics of cluster outbreaks of coronavirus disease 2019 (COVID-19) so as to provide a scientific basis for formulating epidemic prevention and control strategies and measures. Methods Field epidemiological methods were used to survey 41 laboratory-confirmed COVID-19 patients and asymptomatic infected persons involved in 5 cluster outbreaks of COVID-19 from January 24 to February 11 in 2020 in Liaocheng City, and real-time fluorescence quantitative reverse transcriptase polymerase chain-reaction was applied to detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid in the related specimens. Results The secondary attack rate of the initial cases from 5 cluster outbreaks of COVID-19 was 2.78%-50.00%, showing a statistically significant difference (χ2=21.57, P<0.01). 32 cases from 10 families (households) were involved in the family cluster epidemic, while 16 cases from 2 public places in the public place cluster epidemic. There were 5 initial cases, 22 secondary cases and 12 tertiary cases, with the infectious rates being 100%, 18.18% and 0%, respectively. The incubation period of 4 cases was 5-10 days, and the median was 7.5 days. Incubation period transmission was found in the cluster epidemic. 4 (9.76%) cases had a history of travel to or residence in epidemic areas. 30 (73.17%) cases had a history of intimate contact with and frequent conversations with cases in incubation period or confirmed patients. 4 (9.76%) cases were exposed to high concentration aerosol, and the transmission route of 3 (7.32%) cases was unknown. Conclusions SARS-CoV-2 can easily cause the cluster epidemic; and hence, controlling the local cluster epidemic is the focus of prevention and control work. SARS-CoV-2 can be transmitted by high concentration aerosol. The cases in the incubation period are infectious.
2021, Vol. 28 
