Hancock County Indiana Fair H3N2v Cases Acquired N145R
July 13, 2013
The CDC has released H3N2v sequences from the first 12 cases reported in 2013. Five of the sequences are closely related to each other and have collection dates consistent with exposures at the Grant County Fair (see map). All five of these sequences (A/Indiana/04/2013, A/Indiana/05/2013, A/Indiana/06/2013, A/Indiana/07/2013, A/Indiana/08/2013) as well as A/Indiana/19/2013 are closely related to each other and have N145K (due to C483A), which was also in the virulent 2002/2003 Fujian H3N2 strain (which also had D225G).
Two recent papers on H3N2 seasonal flu evolution have cited the association of N145K with significant changes in antigenicity, and the above sequences are the first examples of N145K in H3N2v in human cases. This change may affect the age distribution of H3N2v since the Fujian strain was quickly replaced by the California strain (A/California/7/2004) limiting the number of US citizens exposed to N145K after the 2003/2004 season.
The recently released sequences linked to the Hancock County Fair (A/Indiana/14/2013, A/Indiana/15/2013, A/Indiana/16/2013, A/Indiana/17/2013, A/Indiana/18/2013) with collection dates between 6/29 – 7/1 (see map). These sequences were closely related to each other and the sequences from the Grant County Fair, but had A482G in addition to C483A to produce N145R, which like N145K has not been reported in human H3N2v cases.