Management implications of shifting West Nile Virus transmission suitability in Florida

BackgroundWest Nile virus (WNV), a mosquito-borne flavivirus, has circulated in the USA since 1999. In 2025, Florida was home to 24 million people, with projected increases in population and urbanization in a changing climate. The southern house mosquito, Culex quinquefasciatus, is found in every county, and is a major vector for WNV. Describing shifting WNV transmission risk is important to inform public health and vector control planning. Materials and MethodsUsing published estimates of thermal suitability of WNV transmission by Cx quinquefasciatus, with climate models and population data, we calculated and mapped baseline and projected county-level transmission suitability and people at risk (PAR) for 2000, 2030, and 2050. Five general circulation models (GCMs) and two mitigation scenarios (SSP2-4.5, SSP5-8.5) were used to explore future trajectories. ResultsAt baseline, all 67 counties in Florida experienced 5-9 months transmission suitability. Using the year 2000 census estimates, 2.33 million people in 2 counties experienced 9 months, and in 2030, across climate models, 8.93-12.26 million people (10-20 counties; SSP2-4.5), and 8.95-18.10 million people (11-26 counties; SSP5-8.5) are projected to experience 9 or more months of transmission suitability. In 2050, for both SSP2-4.5 and SSP5-8.5, 17.08-20.42 million people (23-26 counties), ranging to approximately 70% of the projected population of Florida will experience 9 or more months. The 10 most populated counties in 2000 are projected to experience 1-3 months of additional climate driven transmission suitability in the future. ConclusionThe southern house mosquito was previously managed as a seasonal nuisance in Florida but now represents an increasing public health exposure risk. Projections across climate trajectories underscore an increasing suitability and exposure risk for WNV in Florida, ranging as high as around 70% of the population exposed to suitable climate conditions for transmission for 9 or more months of the year in the 2050s. This means the types of operations and number of employees needed in vector control and public health will also increase.