Phylogenetic trees featuring HSV-1 strains which depict the formation of six clades based on geographic origin.

<p>A maximum likelihood (ML) phylogenetic tree was constructed with 31 HSV-1 whole or partial genomic sequences, using HSV-2 as an outgroup. (B) An expansion of the HSV-1 specific node from the ML tree in (A). The ML tree was generated from aligned sequences using the Mega 5 package. Clade I includes European/North American strains, Clade II comprises East Asian strains and III, IV, V and VI are East African. HSV-2 was used as an outgroup. The viral isolates are colored according to country of origin and are as follows: U.S.A: light blue, U.K.: dark blue, China: red, South Korea: purple, Japan: orange, and Kenya: green.