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Paradigm Shift Intervention Monitoring
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Mill Hill released a series
of 2010 sequences
from Argentina and Cameroon. Most of the Argentina sequences were
closely related to a newly emerging sub-clade, which was first seen in Pennsylvania
and Kansas. However, one of the sequences,
A/Argentina/27891/2010, had a region of divergence which had three
consecutive polymorphisms (G1087A, G1089A, T1092C) that match earlier
human H3N2 sequences as well as H3N2 sequences in swine and birds (see
Two of the polymorphisms, G1089A and T1092C were also in two of the
recent trH3N2 sequences found in the United States (A/Minnesota/09/2010
and A/Wisconsin/12/2010), while T1092C was also in two additional
trH3N2 sequences, A/Iowa/16/2009 and A/Pennsylvania/14/2010, (see lists here
In addition to the full HA sequences, Mill Hill also released two partial sequences, and one covered the region described above. That sequence, A/Cameroon/LEID/03/10/227/2010, also had all three polymorphisms. Although the Cameroon sequence was also H3N2, it was not the same sub-clade as the sequences from Argentina, placing this series of polymorphisms on yet another H3N2 background, further supporting acquisition by recombination.
Thus, the tandem changes, G1089A and T1092C are present on three different 2010 H3N2 genetic backgrounds, including trH3N2, in isolates from humans on three different continents (North America, South America, and Africa) .
Theses data increase concerns that trH3N2 is much more widespread in human populations than the five isolates that have been reported from the United States, which highlights the need for more active surveillance and release of sequence data from Canada, Mongolia, and Russia which have reported unusual findings associated with H3N2 infections.