Epidemiological characteristics of transmission of SARS-CoV-2 Delta variant in a farmers'market
Objective To investigate the epidemiological features of spread of SARS-CoV-2 Delta variant in a farmers'market so as to provide a scientific basis for prevention and control of the epidemic caused by SARS-CoV-2 Delta variant in the people-gathering places.Methods Descriptive epidemiological methods were used to describe the epidemiological characteristics of the SARS-CoV-2 epidemic.The incubation period of the cases and time-varying reproduction numbers were estimated and calculated.Results From December 7 to 20,2021,a total of 122 confirmed cases of SARS-CoV-2 infection and 104 asymptomatic infected persons were cumulatively identified in the epidemic.The average age was 49.53 years old,and the ratio of male to female was 0.74∶1.The occupations of the cases were mainly individual vendors(30.97%)and housewives(16.81%).9 townships/streets were involved in the epidemic,mainly occurring in Caoe Street(82.30%)and Baiguan Street(5.75%).The median incubation period of SARS-CoV-2 among the cases in the epidemic was 4 days(with a range of 2-12 days).The time-varying reproduction number was 4.6 during the peak period of the epidemic,and then showed a constantly downward trend,declining to below 1 within 13 days after the occurrence of the epidemic.The epidemic spread in turn among individual vendors,customers and customers'families.The number of SARS-CoV-2 infection cases decreased to 0 within 13 days(from December 7 to 20)since the discovery of the local outbreak,and the main discovery methods were population screenings based on centralized quarantine(45.13%)and self-quarantine at home(39.38%).Conclusion SARS-CoV-2 Delta variant spread very fast in the farmers'market,suggesting that we should quickly identify and isolate the risk population so as to control the spread of the epidemic.