Commentary
H5N1 Spread in Korea Linked to Northeastern Migration?
Recombinomics Commentary 10:54
May 3, 2008
Bird flu outbreaks have spread to six of South Korea's nine provinces despite a massive cull which saw the slaughter of more than five million chickens and ducks last month, officials said Saturday.
An outbreak reported Wednesday at a farm around 300 kilometers (187 miles) southeast of Seoul was confirmed after blood tests as the virulent H5N1 strain of the disease, the agriculture ministry said.
It raised to 23 the total number of outbreaks reported across six provinces of South Korea.
Meanwhile quarantine authorities denied allegations they had covered up an outbreak of avian influenza in the province of North Gyeongsang last month.
Responding to a television report, they said they had been cautious of the results of preliminary tests on poultry at Yeongcheon City, but final results confirmed the outbreak.
The above comments confirm that H5N1 has spread throughout South Korea (see satellite map) and the disclosure of the spread has been delayed by the withholding of test results. This approach is similar to the control efforts by India.
South Korea has defined 11 outbreaks in OIE reports, which have not been filed since the middle of last month. The most recent report, and associated press releases, were careful to draw distinctions between highly pathogenic H5 and highly pathogenic H5N1, when in fact the only difference is the number of confirmatory tests that have been announced. Last season the H5N1 in south Korea was the Uvs Lake strain of H5N1, which is within a sub-clade (2.2.3) of clade 2.2. It is likely that this seasons outbreaks will be related, so the H5N1 will have the HA cleavage site GERRRKKR. Sequencing of the cleavage site is one of the first tests on influenza A positive samples. The series of test are confirmatory in nature. Samples with GERRRKKR will be H5 which will be highly pathogenic H5, which will be highly pathogenic H5N1, which will be clade 2.2 H5N1, which will be clade 2.2.3, which will be the Uvs Lake strain of clade 2.2.3. Thus, the distinction between highly pathogenic H5 and highly pathogenic H5N1 is only administrative, and dependent on the extent of completing a series of confirmatory tests.
These distinctions have been used to delay confirmation that the soldier infected with highly pathogenic H5 is infected with highly pathogenic H5N1.
However, these delays in testing can lead to delays in actions, which leads to an increase in spread. More than 6 million birds have been culled and live market trading has been suspended, but new outbreaks are confirmed as test results are announced.
This record break outbreak in South Korea has been followed by detection of H5N1 in northeastern Japan and southeastern Russia, which may be signaling migration of H5N1 to Alaska, which is likely seeded by the massive outbreaks in South Korea.
Release of H5N1 sequences from Korea, Japan, and Russia would be useful.
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