Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Genetic relationships of human, swine, and avian influenza viruses for N1.
Names represent viruses all containing an N1 and different hemagglutinin types (as indicated). Year of isolation is indicated. The 2007 WHO recommended H1N1 vaccine strain: A/Brisbane/59/2007(H1N1) is underlined. The 2009 pandemic H1N1 (pH1N1) can be found at the top branch of the tree. Scale bar indicates amino acid substitutions per site.
