Environment/Climate Change
Impact of climate variability on projected influenza outbreaks Aleksandra Stamper* Aleksandra Stamper Rachel Baker
Wintertime influenza epidemics consistently account for substantial morbidity and mortality in temperate regions around the globe. The timing of an influenza outbreak is closely tied to seasonality, with epidemics occurring during the winter months in temperate areas. These regions typically experience lower absolute humidity (AH) of the ambient air during winter, creating conditions that previous studies demonstrate to enhance influenza virus survival and transmission. Climate change is expected to alter patterns of extreme weather events, including AH and temperature; however, it remains uncertain how these extremes could affect the timing and severity of the seasonal influenza outbreak. Here, we used a mechanistic epidemiological influenza model, fitted to observational data, to examine the impact of weather extremes on the influenza season.
We adapted the Susceptible-Infected-Recovered model and applied it to Miami, New York, and San Francisco. The model for each location was calibrated using historical weekly influenza incidence and AH data, with the relationship between AH and transmission based on prior experimental data. By introducing a single week of unusually high or low humidity (1st and 99th percentile) at different times during the influenza season, we calculated the projected differences in peak size, timing, and overall magnitude of the anomalous model compared to the base model.
Our findings, presented in the figure, indicate that while abnormally low AH during winter may starkly increase the influenza peak (a projected increase of 18.3% to 35.6% in the proportion of infected individuals), anomalously high wintertime AH may result in a lower peak of infected individuals but a prolonged outbreak period. The framework developed here provides insights into the potential impacts of extreme climate variables on influenza outbreaks, informing public health preparedness and guiding the development of effective mitigation strategies for future epidemics.
