Swine Flu V: Sequence Analysis

Via ProMED-mail: sequence analysis indicates that swine flu may be entirely domestic and porcine, despite previous reports linking it to human and bird flus as well as Asian swine flu strains.

"...the NA and M genes are most closely related to corresponding genes from influenza viruses isolated in swine population in Eurasia."
However, the NA and M genes from 2 swine virus isolates from America are also closely related to the novel H1N1 virus (A/swine/Virginia/670/1987, A/swine/Virginia/67a/1987), if a reasonable nucleotide substitution rate is accepted. Thus, H1N1 from Mexico may be a swine flu virus strain of entirely American origin, possibly even of relatively ancient origin.