Implications of climate variability on norovirus burden and control

Norovirus is one of the most common causes of gastroenteritis in humans being responsible for approximately 1 in 5 cases of acute gastroenteritis, 200,000 deaths per annum, and a global cost of $60 billion. It is highly infectious with a 49% probability of infection from just one viral particle. However, these values are likely underestimated due to underreporting and non-specific symptoms.

Occurrence is highly seasonal with over half of reported cases occurring in winter; though this timing may have been disrupted by non-pharmaceutical interventions (NPIs) in the COVID-19 pandemic. This means seasonal peaks occur simultaneously with increased burden from respiratory pathogens such as COVID-19 and influenza, further exacerbating the strain on healthcare. Yet, the drivers for the seasonality of norovirus are uncertain, encompassing both population and climatic conditions. There has also been little exploration to date on how the occurrence of norovirus is affected by climate change.

Through this project, we will develop mathematical models of norovirus transmission and burden whilst accounting for the mechanisms of seasonality and environmental influence. These models will allow us to examine key factors in the timing of seasonal peaks; how to mitigate the resulting healthcare burden, and how these seasonal patterns may be affected by future disruptions both human-mediated, and through climate variability.

Our modelling will incorporate measures of seasonality by age group and geography to account for differential reporting by subpopulation and climate. We will propagate uncertainty from existing data sources, disentangle the effects of NPIs during the COVID-19 pandemic, as well as use sensitivity analyses to explore unobserved mechanisms for climate-mediated changes in transmission. Finally, we will explore how future climate scenarios may affect norovirus seasonality and occurrence in order to quantify future healthcare system burden and mitigation approaches.