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Commentary
2013 Human and
Swine H3N2v Sequence Discordance
Recombinomics
Commentary 23:45
August 15, 2013
The only Ohio resident with confirmed H3N2 in 2013 had visited a agricultural fair in northwestern Virginia just prior to disease onset.
Similarly no cases have been reported in Minnesota this year although the July 11 isolate, A/swine/Minnesota/A01351603/2013, also matched 2012 human cases.
In contrast to the frequent detection of 2013 swine matches with 2012 human cases, only one swine sequence, A/swine/Illinois/A01432795/2013, isolated in June is closely related to the 2013 human cases, which all have a closely related H3 which has either N145K or K145R (the Illinois swine has N145K). Thus, there is significant discordance between swine sequences, where there is just one closely related to the human sequences, while all 16 human cases in 2012 are closely related even though they are linked to fairs and farms in Indiana, Virginia, and Illinois.
Moreover, the three most recent human cases (A/Ohio/05/2013, A/Illinois/03/2013, and A/Indiana/11/2013) all have an H1N1pdm09 PA gene segment (as well as an M gene segments) which is identical in the isolates from Illinois and Indiana and are virtually identical to the sequence from Virginia (diagnosed and confirmed in Ohio).
This discordance again suggests that humans are infecting swine, which is why the human sequences share changes that are rarely found in swine collections made prior to the fair season.
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