D3031: Site-specific differences in human West Nile virus case prediction accuracy cannot be explained by differences in Culex pipiens and C. restuans community composition using 2021 trapping data from Chicago, Illinois

In the north-central United States, Culex pipiens and restuans, two cryptic mosquito species, serve as the primary WNv vectors between birds and play a role in transmission to humans. The difficulty of differentiating the two species often leads researchers to group them in WNv transmission research, which may blunt epidemiological model accuracy. Human case modeling in Chicago based on grouped data has determined many significant drivers of local human infection in Chicago but does not accurately predict cases across all sites. This uncertainty could stem from patterns in vector community composition that are missed when Cx. pipiens and restuans are pooled. To investigate this, we used PCR-based species identification to determine the relative proportion of these two species for 21 Chicago sites, a subset of those assessed by Karki et al. (2020). We found that differences in the relative proportion of Culex restuans and pipiens could not explain site-specific differences in model accuracy based on Culex collections from the summers of 2021-2. Future work will examine WNv prevalence across both species and years. Outlining this web of phenology, WNv prevalence, cryptic species identity, and geography will allow us to better investigate the hidden factors complicating human case prediction.