Commentary
Vaccine
and Tamiflu Resistant H1N1 in Korea?
Recombinomics Commentary
18:06
January 30, 2009
2,233 viruses were identified as A/H1N1 type and 107 viruses were identified as A/H3N2 type.
The above comments from the week 3 report from South Korea show an increase of 461 H1N1 isolates over levels reported in week 2, which is similar to the week 2 increase of 497 or the week 1 increase of 508. These levels dwarf H3N2 levels (which increased by 25 in week 3), or influenza B levels (which is rarely detected). Thus, about 95% of the reported influenza in South Korea is H1N1 and the frequency of Tamiflu resistance is near 100%.
Tamiflu resistance is also near 100% in Japan, but the levels of H3N2 and influenza B are markedly higher, so the resistance is in about 1/3 of cases. However, Japan has seen a doubling of reported cases in the past week and has issue a nationwide alert, leading to many school closings. Earlier this season, school closings were linked to H1N1 outbreaks and the H1N1 isolated from those outbreaks was similar to the H1N1 in the United States, which has a number of receptor binding domain changes, including A193T.
This change is also likely in Europe, where H274Y levels in H1N1 also approach 100% and the recent update from Italy indicated three of the first five isolates were from patients who had been vaccinated this season. The data raise concerns that the Tamiflu resistant H1N1 is also resistant to the current H1N1 vaccine, which targets Brisbane/59. Although the Tamiflu resistance is in the Brisbane/59 sub-clade 2B, the vaccine target was isolated in 2007, and the current clade 2B in circulation has a number of NA and HA changes that has led to the fixing of H274Y. To avoid the natural immunity that developed last season, the H1N1 acquired these additional changes, some of which were in clade 2C.
As more cases of flu are reported, the emerging H1N1 with H274Y may become increasingly problematic. Japan had a large number of school closings in late 2008 linked to H1N1, and nationwide alerts have been issued due to the jump in cases. Levels have also been high in Korea, raising concerns that the resistance levels in Asia will increase the likelihood of dual infections involving H5N1 and H1N1 in China, where both serotypes are circulating leading to H5N1 with H274Y.
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