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Region-specific surveillance may be best for influenza A(H5N1)
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Results of a large-scale genetic analysis demonstrated that the migration patterns for highly pathogenic avian influenza A(H5N1) follow a global persistence model with each of the nine regions studied acting as a disease source. Understanding global migration patterns may aid disease surveillance and prevention, researchers said.
“Our results call for reassessment of the role of each geographic region in the migration network and in the genetic source of [highly pathogenic avian influenza (H5N1)] viruses and suggest that region-specific surveillance policies and vaccine candidate selection strategies should be considered,” they wrote.
The researchers performed a genetic analysis of 3,365 highly pathogenic avian influenza A(H5N1) viruses. They divided the sequences into nine regions: China; Hong Kong Special Administrative Region; South Korea and Japan; Siberia; Southeast Asia; southern Asia; western and central Asia; Europe; and Africa.
These regions are all connected in a global migration network, according to the researchers. The analysis showed that Siberia is the most active, with the highest emigration rate and the second highest immigration rate of the nine regions.
“Siberia seems to play a vital role in this migration network, connecting Europe, central and western Asia, and South Korea and Japan,” they wrote. “This finding is consistent with the fact that multiple bird migration flyways intersect in Siberia; the region is also one of the most commonly used breeding sites and in summer contains a high number of wild birds.”
Since 2004, southern China has been considered a major source for the evolution and variation of the virus. However, according to these results, Southeast Asia and Africa are also major sources of genetically and antigenetically novel influenza A(H5N1) virus variants.
“The role of these regions as genetic reservoirs for subtype H5N1 viruses is underscored by the higher genetic diversities of viruses in these regions compared with those of other regions,” the researchers wrote. “Therefore, increased sampling from Southeast Asia and Africa is vital for understanding the global dynamic of HPAI (H5N1) viruses.”
Understanding the different migration dynamics between avian and human influenza viruses might facilitate region-specific surveillance and help researchers select the most appropriate vaccine candidates, they concluded.
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