Commentary
Guangdong H5N1 Raises Global Expansion Concerns
Recombinomics Commentary 08:59
June 18, 2008
A Hong Kong factory owner based in Yashan said yesterday that most of the duck farmers in the village were from Zhejiang province, rather than locals, and dozens of them bred fish and ducks together.
"I've heard of massive deaths of ducks for several days. Initially, farmers were reluctant to report the case to the local agriculture and fisheries department but, when the virus spread, they could no longer cover it up any more and the officials came," the factory owner said.
The above comments suggest that the recently reported fatal H5N1 infections in ducks in Guangdong province may be more widespread in China. The recent reports on H5N1 positive dead ducks in Jiangmen is not a surprise since H5N1 was recently reported in Hong Kong for the first time in five years. However, the H5N1 in Hong Kong was in asymptomatic chickens, while the H5N1 in Jiangmen, (see satellite map) and additional areas in China is from dead ducks. It is unclear if this difference is linked to changes in the H5N1 or difference in the vaccination status of infected flocks.
Although no recent H5N1 sequences have been released from Hong Kong or southern China, sequences have been published from recent outbreaks in Japan and Russia. The published sequences are almost identical and are said to also be closely related (over 99.7%) to sequences in South Korea.
The HA sequences, which are clade 2.3.2 (Fujian subclade), appear to be closely related to A/common magpie/Hong Kong/5052/2007, based on mapping location in the phylogenetic tree published in the WHO report on H5N1 vaccine targets. The other seven gene segments in the 2008 published sequences are clade 2.3.4 and most closely related to A/China/GD02/2006, which is from a patient in Guangdong province, which provides additional indirect evidence that the H5N1 circulating in Hong Kong is a similar reassortant.
The widespread outbreaks in Hong Kong, followed by the confirmation in Guangdong province adds evidence for a global expansion of the clade 2.3, since it now has been confirmed in long range migratory birds in Japan, which is also the likely source for the H5N1 in Russia and South Korea.
The linkage to Hong Kong provides evidence for transport along the Australia East Asia Flyway and suggests Fujian H5N1 may have already migrated to North America.
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