Management implications of shifting West Nile Virus transmission suitability in Florida

Background : West Nile Virus (WNV), a mosquito-borne flavivirus, has circulated in the USA since 1999. In 2025, Florida is 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 known vector for WNV. Describing shifting WNV transmission risk is important to inform public health and vector control planning. Materials and Methods : Using 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 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. Results : At baseline, all 67 counties in Florida experienced 5-9 months suitability. Using the year 2000 census estimates, 2.33 million people in 2 counties experienced 9 months of suitability. In 2030, across 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, 12.51-20.42 million people (18-26 counties; SSP2-4.5), and 17.08-20.42 million people (23-26 counties; SSP5-8.5) will experience 9 or more months. The 10 most populated counties in 2000 are projected to experience 1-3 months of additional transmission suitability in the future. Conclusion : The 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. This means the types of operations and number of employees needed in vector control and public health will also increase.