Phylogenetic Analysis of St. Louis Encephalitis Virus within Two Southwestern United State Counties: a case for a bulk introduction event into the southwest United States

摘要: St. Louis Encephalitis Virus (SLEV) has been seasonally detected within the Culex spp. populations Maricopa County, Arizona and Coachella Valley, California since an outbreak in County 2015. Previous work revealed that was caused by importation of SLEV genotype III, which had only Argentina prior years. However, little is known about when occurred or population dynamics its arrival into southwestern United States. In this study, we wanted to determine if annual detection Riverside counties due enzootic cycling new importations. To address question, analyzed 143 genomes (138 sequenced as part study) using Bayesian phylogenetic analysis software, BEAST, estimate date American Southwest characterize underlying structure SLEV. Phylogenetic clustering showed variants circulating form two distinct with evidence transmission among onset outbreak. Interestingly, Valley appear be annually imported from a nearby source, whereas locally sourced each year. Finally, earliest representatives III US formed polytomy includes both samples. We propose initial could have resulted introductory SLEV, perhaps one more bird flocks migrating north 2013, rather than single variant introduced bird.