South Korea Bangladesh and India H5N1 Levels Raise Concerns
Recombinomics Commentary 18:04
April 20, 2008
The latest H5N1 reports out of South Korea indicate H5 has been confirmed at 25 locations (which are almost certainly H5N1), and 21 additional sites are under investigation. Almost 5 million birds have been culled, suggesting that the H5N1 outbreak this month will be at record levels.
Recently, similar reports came out of Bangladesh and India. Although H5N1 in Bangladesh has been reported for over a year, the number of infected farms and level of culling increased dramatically in the spring. The same has been true for India (West Bengal and Tripura). All of these areas are close to major wetlands, including the Ganges Delta in Bangladesh and West Bengal. In South Korea the same regions in southwestern Korea (see satellite map) are affected year after year, which lie under a migratory bird flyway between South Korea and Mongolia.
These reports of record levels of H5N1 in these areas raises concerns that as wild birds fly to common nature reserves at the intersections of major flyways, the H5N1 from each region will recombine and generate more genetic diversity, which will the spread south in the fall.
Included in these new combinations are receptor binding domain changes, which have been widely reported in clade 2.2, especially in human cases in the Middle East. Moreover, vaccine resistant strains in Egypt have acquired a large number of non-synonymous changes, which will also be migrating north in the upcoming weeks.
The repeated and record outbreaks in South Korea may have led to the decision in Japan to implement a pre-pandemic vaccine strategy involving first responders, as well as 10-20 million citizens, which may also lead to an increase in vaccine doses.
Stockpiling vaccines makes little sense because H5N1 is constantly evolving away from the early vaccine targets, and this evolution is along multiple parallel pathways.
These changes highlight the need for more active surveillance. However, the detection of H5N1 in farms prior to the detection in wild birds points toward failed surveillance systems, which limits the predictability of the changes because of gaping holes in the sequence database.
The increasing pace of H5N1 evolution highlights the need for a more robust surveillance system. as well as the likelihood of a major pandemic sooner rather than later.
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