S-OIV = 2009 Influenza A H1N1 Virus = swine flu virus

As more cases appear, the name of the virus is also undergoing mutation. The translation of "porcino" to "swine" was, admittedly, an unfortunate one. The suggestion to call it "Mexican flu virus" was politically incorrect. The final acronym might end up becoming "SOIV", after a further deletion of the unpronounceable dash.

CDC communications have starting to refer to the virus as "swine-origin influenza A (H1N1) virus (S-OIV)", including yesterday's must read MMWR article "Outbreak of Swine-Origin Influenza A (H1N1) Virus Infection --- Mexico, March--April 2009". In the analysis described there, a probable case was defined as a suspected case who tested positive for influenza A, presumably by a direct antigen test. Yet we know that these tests only have around 50% sensitivity for seasonal flu viruses, and that the sensitivity for SOIV might be even lower. Accumulating data on the value of rapid antigen test results to predict a positive PCR test result will determine whether or not the suspect/probable case classification should be based exclusively on the antigen test result.

The CDC issued guidelines for dismissal of schools and childcare facilities, addressing the issue of my previous blog.

In the meantime, some light is being shed on the origin of SOIV, as sequence data becomes available.