Overwintering of WNV in southern CA. (A) The MCC phylogeny of WNV, with the areas of interest highlighted. (B) A close-up view of one branch from the MCC phylogeny, with winter isolate COAV179_2011 highlighted. (B) A close-up view of another branch from the MCC phylogeny, with winter isolate GRLA6143_2007 highlighted. Isolate names include location of collection, isolate number, and date of collection in decimal format.
WNV was introduced into California at least 5 times.
The SW03 genotype of WNV was constrained to southern California.
The SW03 genotype spread with a more rapid dispersal rate than the WN02 genotype.
The overall dispersal rate of WNV has decreased dramatically since its emergence.
WNV overwintered in California in Culex mosquitoes.