33 - A Spatially Resolved and Environmentally Informed Forecast Model of West Nile Virus in Coachella Valley, California

Abstract: West Nile virus (WNV) is the most significant arbovirus in the United Staes. West Nile exists in a complex transmission cycle between avian hosts and the arthropod vector, Culex spp. mosquitoes. Human spillover events occur when humans, a dead-end host, are bitten by an infected mosquito. Predicting infectious mosquitoes and therefore the risk of transmission to humans is associated with fluctuations in environmental conditions. In this study, we used a multi-model inference systems to look at how changes in hydrological and meteorological conditions were associated with mosquito with mosquito infection rates of WNV in the Coachella Valley of California. We developed and tested a spatially resolved ensemble forecast model of the WNV mosquito infection rate in the Coachella Valley using 17 years of mosquito surveillance data and North American Land Data Assimilation System-2 environmental data. Our multi-model inference system indicated that the combination of a cooler and dryer winter, followed by a wetter and warmer spring, and a cooler-than-normal summer was most predictive of the prevalence of West Nile-positive mosquitoes in the Coachella Valley. We have since employed this system to make seasonal and real-time predictions for 2023 and 2024. In real-time, our model was accurate 70 % of the time with a sensitivity of 27 % and a specificity of 1. In 2024, the model initially predicted high infection rates over the season, but when informed with temperature data from July (~2.5 SD > historical average) it correctly predicted the observed cessation in transmission seen in August (~ week 33). Environmentally informed early season predictions of West Nile risk performed better than the null model; thus, integrating environmental conditions into the disease transmission process has the potential to allow local abatement districts and public health entities to implement more timely abatement interventions and risk mitigation for human transmission.