Evidence for an Overwintering Population of Aedes aegypti in Capitol Hill Neighborhood, Washington, DC.

Aedes aegypti is an invasive, highly anthropophilic mosquito and a major vector for dengue and chikungunya. Population persistence in the continental United States is reportedly limited to southward of the average 10°C winter isotherm, which in the east, bisects Alabama, Mississippi, Georgia, and South Carolina. We report on summer collections and genotypic analyses of Ae. aegypti collected in the Capitol Hill neighborhood in Washington, DC (WDC). Analysis of a 441-bp fragment of the mitochondrial cytochrome oxidase I gene sequence identified the same two haplotype sequences during 2011-2014, and placed these within two discrete groups known to be derived from lineages resident in the Americas. Analysis of 10 microsatellite loci for specimens collected during 2011-2014 revealed no evidence for introgression of new alleles across years. Overall, our data support a conclusion that this represents a resident WDC population, likely maintained during winter months in a subterranean habitat that facilitates year-round survival.