Fig 1. Emergence of WNV in New York.

Though WNV was first detected in New York in 1999, (A) it likely became established in 1998 (confidence interval = October to December 1998) (B) by an introduction possibly from the Middle East, although the exact location cannot be inferred. Data from specific times can be visualized on Nextstrain using the “Date Range” function. A live display can be found at nextstrain.org/WNV/NA?c=num_date&d=tree,map&dmax=1998-12-01&p=grid.