Surprisingly severe flu season

This flu season is starting to rival the pandemic of 2009 in number of people infected. This is surprising because the strain reported to be causing most of the infections is said by the CDC not to have changed significantly. Usually, a big increase in flu outbreaks after years with mild outbreaks is associated with a new strain of virus.

It is too soon to say whether severe illness and deaths will be signicantly higher this year. This is because deaths lag infections by weeks to months.


2 thoughts on “Surprisingly severe flu season

  1. Actually, the severity of the current flu season is not a surprise. In week 48 the CDC cited two H3N2 “low reactors” and they have released the sequences for both. One, A/Hawaii/29/2012, has a significant HA change, L157S, and the CDC has already selected a earlier isolate, A/Hawii/22/2012, (which is virtually identical and has L157S) for testing as an H3N2 vaccine target. The other low reactor, A/Iowa/14/2012, has T128A, which abolishes the glycosylation site at position 126. This same change emerged in the H3N2 Fujian strain in 2003/2004 flu season, which was severe and produced a signaificant number of pediadric deaths (leading to US regulations making pediatric deaths reportable).

    The media myth on the H3N2 vaccine match in 2012/2013 is described here

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