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.
Reference sequences of strains circulating in 2009–2015 are presented in italics (GISAID numbers are provided). Influenza strains of patients with severe infection are reported with a black circle and strains from patients with a mild infection are reported with a white circle. Bootstrap values are given at nodes, and the scale bar is given in numbers of substitutions per site.
