Study of asymptomatic norovirus infection in kitchen workers in key places in Tongzhou district, Beijing, 2019−2021

  Objective   To investigate the prevalence of asymptomatic norovirus infections status in kitchen workers in schools, child care settings, and catering service units and other key places in Tongzhou district of Beijing from 2019 to 2021, and provide evidence for scientific prevention and control of norovirus infection.

  Methods   The simple random sampling method was used to select the kitchen workers, especially the kitchen workers preparing cold dish, from catering service units, schools, childcare settings, construction sites, hotels as study subjects,and their anal swabs or stool samples were collected for norovirus nucleic acid detection by fluorescence quantitative PCR. Descriptive method was used to analyze the asymptomatic norovirus infection status of the kitchen workers.

  Results   A total of 3880 samples were collected from 552 units, and 15 norovirus positive cases were detected, including 1 sample positive for GⅠ and 14 samples positive for GⅡ. The asymptomatic norovirus infection rate was 0.39% (15/3880),in which 0.30% (5/1656) in man, and 0.45%(10/2224) in women. No asymptomatic infections were detected in age groups ＜ 18 years and ＞ 60 years, and 2055 cases were detected in age group 19− years, with a positive rate of 0.34% (7/2055), and 1637 cases were detected in age group 46− years, with a positive rate of 0.49% (8/1637). In 2019 when no COVID-19 epidemic occurred, the asymptomatic norovirus infection rate was 1.00% (1/100), but the asymptomatic norovirus infection rate was 0.39% (11/2805)in 2020 and 0.31%(3/975)in 2021 in the context of COVID-19 epidemic.

  Conclusion   The asymptomatic norovirus infection rate in kitchen workers in key places in Tongzhou was similar to the average level in Beijing during the same period. In COVID-19 epidemic period, the asymptomatic norovirus infection rate was lower than that before the epidemic.