2013 Guizhou H5N1 Sequences Match 2012 Fatal Case
Recombinomics Commentary 19:30
February 25, 2013

The WHO Chinese National Influenza Center has released H5N1 sequences (at GISAID) from two recent cases in Guizhou Province. The agency is to be commended for the rapid release of these important sequences (full sequences for all gene segments except PB2). One set was from a fatal case (21 years old), A/Guizhou/1/2013, with a collection date of February 8, which would match the recently described fatal case (21F). The second sequence (A/Guizhou/2/2013) was from a February 9 collection from a 31 year old, which would match the case (31M) who recently died. Initial reports cited an absence of contact with poultry.

Both of the 2013 sequences are closely related to each other as well as the 2012 fatal case (39M) from Guizhou, A/Guizhou/1/2012. The H5 sequence from the 2012 has been described. It had a number of receptor binding domain changes flanking position 190 (A188E, A189T, T199I, I202V), as well as a cluster of changes around S133L. All of these features, which were noted in the 2012 sequence, are also present in the two 2013 sequences. All three sequences also gained a glycosylation site due to T219N.

Although these features are found in the three human sequences from 2012 and 2013, these combinations of changes are not found in any recent poultry sequences. A BLAST analysis of the H5 sequence, as well as the other 6 segments, yields closest relationships with H5N1 sequences from isolates collected 5-7 years ago.

The absence of matching poultry sequences, and the close relationship between all three human sequences, which had a more than 1 year gap between the 2012 isolate and the two from 2013, raise serious concerns over surveillance or human to human transmission.

A clarification on poultry exposure and the H5 status and sequence of such exposures would be useful.