Michigan H3N2v With H1N1pdm09 PA & MP
September 3, 2013
The CDC has released a full set of H3N2v sequences from the Michigan case (6M) who exhibited swine at the Berrien County Fair in southwestern Michigan (see map). The case was diagnosed in Indiana and named A/Indiana/21/2013. As expected, the sequence was closely related to the three most recent sequences (A/Ohio/05/2013, A/Illinois/03/2013, A/Indiana/11/2013) and had H3 N145K as well as H1N1pm09 PA and MP gene segments.
Thus, all four of the most recent cases (with collection dates between July 21 and August 22) have an H1N1pdm09 PA gene segment which is virtually identical to each other. These four cases are linked to agricultural fairs in Virginia, Illinois, Indiana, and Michigan.
However, the CDC has not addressed in the presence of H1N1pdm09 PA gene in the four most recent cases, although its presence is noted in the characterization sheet for each of the four cases. The presence of H1N1pdm09 PA signals further human adaptation and raises concerns regarding limited surveillance and sub-typing of summer influenza A cases not linked to swine or agricultural fairs.