Unique Strain in Mexican Swine Flu Virus Raises Concern But Confirmed American Cases Were Milder Than Mexican Episodes

The CDC is expressing concern over the unique combination of viruses in the current Mexican and Californian swine flu cases which have been determined to be 'closely related' according to a report from the Center for Infectious Disease Research and Policy after a MMWR dispatch at "Human swine flu cases with unique strain raise concern ".

The worrying part is shown in an excerpt from the CDC's dispatch :

Preliminary genetic characterization of the influenza viruses has identified them as swine influenza A (H1N1) viruses. The viruses are similar to each other, and the majority of their genes, including the hemagglutinin (HA) gene, are similar to those of swine influenza viruses that have circulated among U.S. pigs since approximately 1999; however, two genes coding for the neuraminidase (NA) and matrix (M) proteins are similar to corresponding genes of swine influenza viruses of the Eurasian lineage (1). This particular genetic combination of swine influenza virus segments has not been recognized previously among swine or human isolates in the United States, or elsewhere based on analyses of influenza genomic sequences available on GenBank.* Viruses with this combination of genes are not known to be circulating among swine in the United States; however, no formal national surveillance system exists to determine what viruses are prevalent in the U.S. swine population. Recent collaboration between the U.S. Department of Agriculture and CDC has led to development of a pilot swine influenza virus surveillance program to better understand the epidemiology and ecology of swine influenza virus infections in swine and humans.

The CDC also notes:

Because these viruses carry a unique combination of genes, no information currently is available regarding the efficiency of transmission in swine or in humans. Investigations to understand transmission of this virus are ongoing.

So they're a little worried there, but still it's a flu, and they know the basics of flu.

In regards to the identified swine flu victims in the US they are recovering, not dying like so many in Mexico though they have very similar strains of swine flu. Even more so, the known virus sufferer have relatives who had flu like symptoms, but apparently even milder cases of flu around the time of the subjects' infections and all the relatives recovered. The relatives weren't tested apparently because they didn't go to the doctor for treatment.  (I'm calling the cases 'mild' as compared to the problems in Mexico though, the reporting here makes it seem that it's a pretty nasty bug compared with the usual infections that come through in the winters.) And the important point with the American swine flu cases like with the Mexican version is that they seem to have been transmitted between people since contact with pigs was absent with both patients, though one had attended a fairground on which pigs were housed with in a month of catching the flu.

The CDC report also notes that cases of swine flu in humans have been increasingly more frequent in the last decade and warns doctors to test a whole class of flu types to help track the possible types.

tags: swine flu  california  mexico  cdc  

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