Maintenance and variant circulation of St. Louis Encephalitis virus in the American southwest
St. Louis Encephalitis (SLE) was the biggest epidemic mosquito-borne viral disease in the United States until West Nile virus was introduced in 1999. In 2015, the US saw an outbreak of SLE with 23 human cases, all of which were in Arizona, signaling a reemergence of the St. Louis Encephalitis virus (SLEV) in the southwest. Since then, cases of SLE have been on the rise in the American Southwest, with 32 cases being reported in 2022, and the states of Arizona and California seeing a large proportion of those cases. SLEV has been detected in Maricopa County, AZ and Riverside County, CA every year since 2015, and with this project we aimed to better understand the phylogenetic relationship of the virus between these locations, as well as others in the southwest. 92 SLEV genomes from mosquito pools collected from Maricopa County and Riverside County, in 2022, were sequenced and a phylogenetic tree revealed that SLEV from Maricopa County and Coachella Valley are not linked. By tracking the maintenance and variant circulation of SLEV, we are able to aid public health agencies in these areas by helping them target their mosquito population mitigation strategies and inform the public when infection risk is elevated.