Assessment on transmission capacity of norovirus infection and effect of control measures in schools

  Objective   To estimate the transmission capacity of norovirus infection and to evaluate the effect of measures for norovirus infection epidemic control in schools for providing evidences to the development of relevant management strategies and control measures.

  Methods   From Shenzhen Municipal Information System for Disease Control and Prevention, we extracted data on 53 epidemics of norovirus infection from 2015 through 2019 in schools in Futian district of Shenzhen city. The susceptible-exposed-infectious-removed (SEIR) dynamics model was used to simulate the collected data for the calculation of basic regeneration coefficient (R₀) of the epidemics to evaluate the epidemic transmission capacity and calculations of cumulative incidence rate and duration of the epidemics to evaluate the effect of control measures.

  Results  For the occurred epidemics under the condition without any intervention, the basic regeneration coefficient (R₀) of norovirus infection was 11.54 (25% percentile: 10.52, 75% percentile: 13.60). There was no significant difference in R₀ between different years, between epidemic season and non-epidemic season, and among different types of schools (all P > 0.05). Compared to the outbreaks in schools without class suspension, significantly lower cumulative incidence (Z = 8.875, P < 0.001) and shorter epidemic duration (Z = 8.172, P < 0.001) were observed for the outbreaks in the schools with 3-day class suspension. The R₀ of the outbreaks with the infected students vomiting in classrooms was higher than that of the outbreaks without the students vomiting in classrooms (Z = 5.523, P < 0.001); the R₀ of the outbreaks in which the attendant students being asked to leave the classrooms when conducting disinfection treatment on the infected students′ vomitus was significantly lower than the outbreaks in which the students being not asked to leave the classrooms when performing the disinfection treatments (Z = 2.893, P = 0.003).

  Conclusion   The transmission capacity of a norovirus infection outbreak in schools is high and the transmission capacity could be effectively reduced by implementing class suspension in and persuading the students to leave the classrooms when conducting disinfection treatment on the infected students′ vomitus in the impacted schools.