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Commentary
Fatal
and Severe
H1N1 Cases In Mexico Increase
Recombinomics
Commentary 18:50
April 1, 2011
Confirmed cases of influenza, by age group, under four a range of 15 to 24 years, eight to a group of 25 to 44 and five more to an age ranging between 45 and 64 years of age.
The above translation provides additional detail on the updated list of H1N1 confirmed cases in Mexico. Over half were hospitalized or died, raising concerns that the H1N1 involved in these cases represents a more virulent sub-clade and may have a significantly difference sequence than the sub-clades described previously. Similar frequencies were seen in the cases from the Juarez Traffic Department where most cases are not yet confirmed. The cluster has grown to five including two deaths and one critical case. Thus, that cluster also has more than half of the cases hospitalized with at least half of hospitalized patients dying.
Although it is not clear how representative the confirmed H1N1 cases and/or traffic department cluster are, prior to these latest cases the flu season in Mexico was ending. Most cases were H3N2 which peaked in December, with a minimal number of cases being reported by March. This spike in cases, as well as the virulence of the virus, has raised concerns about the start of a new wave represented by a distinctly different H1N1 which has escape immunological responses to earlier infections or vaccinations and has become more virulent.
Earlier reports suggested the current outbreak in northern Mexico originated in New Mexico and Texas. The influenza levels in these states and throughout the US are declining, but the older sub-clade and H3N2 would mask the rise of a new sub-clade.
Although it is likely that the new sub-clade will be easily identified by sequence and phylogenetic analysis, the CDC has withheld US H1N1 sequences from this season, including almost all isolates collected in 2011. H3N2 and influenza B sequences were released last week and the H1N1 sequences are long overdue and should be released immediately, along with sequences from severe and fatal cases in northern Mexico.
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