H3N2 California 7 Spreading and Evolving Rapidly Worldwide
Recombinomics Commentary
February 25, 2005
Antigens A/Wyoming/3/2003 A/Wellington/1/2004 A/California/7/2004
A/Wyoming/3/2003 1280 640 320
A/Wellington/1/2004 320 1280 320
A/California/7/2004 160 160 640
Recent isolates
A/Singapore/55/2004 320 320 640
A/Victoria/513/2004 640 320 1280
A/Guangzhou/216/2004 640 320 640
A/North Carolina/5/2004 640 160 640
A/Bangkok/2814/2004 40 640 640
A/Singapore/68/2004 160 160 320
A/Dakar/76/2004 160 160 320
A/Wisconsin/19/2004 80 160 640
A/New York/55/2004 80 80 320
A/Lisbon/5/2005 160 160 640
A/England/305/2005 160 80 320
A/Denmark/2/2005 160 80 640
A/Iceland/1/2005 80 160 640
The serological data above shows that A/California/7/2004 has now spread worldwide. The most recent isolates in 2005 (A/Denmark/2/2005 and A/Iceland/1/2005) have larger differential titers with the earlier isolates, A/Wyoming/3/2003 and A/Wellington/1/2004, than with California itself. Thus, the virus not only is spreading rapidly, but also quickly evolving away from A/Wyoming/3/2003 and A/Wellingtom/1/2004.
The rapid evolution of H3N2 subtypes may indicate that vaccines that follow the viral evolution may be losing ground. For the H3N2 component of the trivalent human vaccine A/Panama/2007/99 was used for five years in the Northern Hemisphere. A/Fujian/411/2002 first appeared in 2002. However, because of manufacturing difficulties, Panama was used again in 2003. This year Fujian was used but H3N2 subtypes were already evolving away from Fujian. Wellington will be used this year for the Southern Hemisphere followed by California for the Northern Hemisphere.
However, the virus is evolving rapidly and some of the genes in the earlier H3N2 isolates from New York show signs of recombination, signaling more rapid evolution.
This may indicate new vaccines will have to be created at a faster pace or against more evolved sequences.
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