Consensus and uncertainty in the geographic range of Aedes aegypti and Aedes albopictus in the contiguous United States: Multi-model assessment and synthesis.

Aedes (Stegomyia) aegypti (L.) and Ae. (Stegomyia) albopictus (Skuse) mosquitoes can transmit dengue, chikungunya, yellow fever, and Zika viruses. Limited surveillance has led to uncertainty regarding the geographic ranges of these vectors globally, and particularly in regions at the present-day margins of habitat suitability such as the contiguous United States. Empirical habitat suitability models based on environmental conditions can augment surveillance gaps to describe the estimated potential species ranges, but model accuracy is unclear. We identified previously published regional and global habitat suitability models for Ae. aegypti (n = 6) and Ae. albopictus (n = 8) for which adequate information was available to reproduce the models for the contiguous U.S. Using a training subset of recently updated county-level surveillance records of Ae. aegypti and Ae. albopictus and records of counties conducting surveillance, we constructed accuracy-weighted, probabilistic ensemble models from these base models. To assess accuracy and uncertainty we compared individual and ensemble model predictions of species presence or absence to both training and testing data. The ensemble models were among the most accurate and also provided calibrated probabilities of presence for each species. The quantitative probabilistic framework enabled identification of areas with high uncertainty and model bias across the U.S. where improved models or additional data could be most beneficial. The results may be of immediate utility for counties considering surveillance and control programs for Ae. aegypti and Ae. albopictus. Moreover, the assessment framework can drive future efforts to provide validated quantitative estimates to support these programs at local, national, and international scales. Author summary Aedes aegypti and Ae. albopictus mosquitoes can transmit dengue, chikungunya, yellow fever, and Zika viruses, yet because of limited data the edges of the geographic range of these important species remain uncertain. We assessed numerous previously published model-based estimates of the range of these mosquitoes in the United States and combined those models to produce calibrated estimates of the probability of finding each mosquito in each county. Comparing these estimates to county-level data, we found that there are areas of substantial uncertainty and specific areas where model-based predictions do not align well with available data. The results provide specific information that can help guide national- or state-level efforts to monitor and control Ae. aegypti and Ae. albopictus. Beyond the specific findings, this approach to leveraging limited data and multiple quantitative models can be employed in other settings to better characterize the distribution of these species and other medically important vectors globally.