Influence of climatic factors on the outbreaks of acute gastroenteritis caused by norovirus in China

Objective To investigate the influence of climatic factors on the outbreaks of acute gastroenteritis caused by norovirus (referred to as "human norovirus outbreaks") in China, and to provide a scientific basis for formulating precision prevention and control measures.

Methods Daily case reports and daily meteorological data during human norovirus outbreaks in China from 2012 to 2018 were collected, and the distributed lag non-linear model (DLNM) was used to identify the association between human norovirus outbreaks and main climatic factors.

Results From 2012 to 2018, a total of 964 human norovirus outbreaks were reported in China, with 50 548 cases of infection in total. Human norovirus outbreaks in China showed seasonal characteristics of a higher incidence rate in winter and spring. DLNM analysis results showed that temperature and humidity were negatively correlated with human norovirus outbreaks, and the highest health risk of human norovirus outbreaks was observed at a daily mean temperature of -10 ℃ (risk ratio RR=2.18, 95% confidence interval CI: 1.34-3.56), while the highest relative risk of human norovirus outbreaks was observed at a mean relative humidity of 17% (RR=1.16, 95% CI: 1.01-1.34). Precipitation was positively associated with human norovirus outbreaks, and the RR was the highest when daily cumulative precipitation reached 100 mm (RR=5.10, 95% CI: 1.70-15.36). In addition, stratified analysis implied that high average daily temperature and low relative humidity in the warm season and low average daily temperature in the cold season would increase the risk of a 7 d cumulative lag of human norovirus outbreaks.

Conclusion The climatic conditions of high temperature and humidity in the warm season and low temperature in the cold season are conducive to the spread of norovirus in the population. In the context of climate change, it is necessary to comprehensively consider the health impact of climatic factors on human norovirus outbreaks and formulate targeted prevention and control strategies, so as to reduce the disease burden caused by acute gastroenteritis due to norovirus infection.