Evaluation of the transmissibility of norovirus and the effectiveness of prevention and control measures for schools in Jiangsu Province

Abstract

Objective: This study aims to estimate the transmissibility of norovirus outbreaks in schools by different transmission routes, and to evaluate the effects of isolation, school-closure and disinfection measures under different intervention intensities, finally, scientific prevention and control suggestions are proposed.

Method: 23 outbreaks of norovirus infectious diarrhea occurring in Jiangsu Province's school from 2012-2018 were selected and fitted to the model. The data includes various types of school places and pathogen genotype. A 'SEIAQRW' model with two transmission routes was established. The transmissibility of each outbreak was assessed using effective reproduction number, the efficacy of different intervention measures and intensities were evaluated by calculating the total attack rate and peak incidence.

Results: The mean effective reproduction number of noroviruses was estimated to be 8.92 for the human-to-human route of transmission and 2.19 for the water or food-to-human route of transmission. When all symptomatic cases were isolated, the median peak incidence for both transmission routes both being less than 1.8%. There was a smaller reduction in total attack rate compared to peak incidence, the median total attack rate for the two transmission routes decreased by 17.59% and 42.09%, respectively. When the effect of school-closure or disinfection is more than 90%, the total attack rate and peak incidence in the human-to-human route are reduced by more than 90% compared to no intervention, and the peak incidence in the water or food-to-human routes can be reduced to less than 1.4%, but the reduction in the total attack rate is only 50% or so.

Conclusion: Norovirus outbreaks have a high rate of transmission in schools. In the case of norovirus outbreaks, isolation should be complemented by other interventions, and the implementation of high-intensity school closures or disinfection of the external environment can be effective in reducing the spread of the virus.

Keywords: Norovirus; peak incidence; total attack rate; transmissibility.

Figure 1.

Flowchart of the SEIAQRW model for norovirus outbreak.

Figure 2.

Epidemiological characteristics of 23 norovirus outbreaks. Intervention A means: quarantine and treatment + health education + strengthen disinfection; Intervention B means: Intervention A + morning check; Intervention C means: Intervention B + cancel public activities; Intervention D means: Strengthen the management of canteens and drinking water hygiene.

Figure 3.

Calculation of R_eff for various virus genotypes or places under two transmission routes. P-P means human-to-human transmission route, W-P means water or food -to-human transmission route, and 1–5 in categories of places mean kindergarten, primary school, middle school, Common Colleges and Secondary vocational school, and nine-year school and twelve-year school, respectively.

Figure 4.

TAR simulation results under different interventions in two transmission routes. When the abscissa is 0, it means that there is no intervention. Details of these three parameters are shown in Table 1.

Figure 5.

PI simulation results under different interventions in two transmission routes. When the abscissa is 0, it means that there is no intervention. Details of these three parameters are shown in Table 1.

Figure 6.

Sensitivity analysis results of SEAIQRW model.