Commentary
Global Expansion of Fujian H5N1 Confirmed
Recombinomics Commentary 20:41
May 23, 2008
The match between the Fujian H5N1 sequences in Primorsky, Russia with multiple sequences from northern Japan and the record outbreak in South Korea leaves little doubt that a global expansion of Fujian clade 2.3 sequences has begun. H5N1 has never been reported in northern Japan or southeastern Russia and prior outbreaks in South Korea and Japan have been at the end of the year when birds are migrating into the region. The current outbreaks are in the spring, when birds are migrating out of the region.
The tracks of outbreaks (see satellite map) signal movement to the north and will likely migrate Fujian H5N1 into new regions. Although such movements may have happened previously, but not detected, the record levels in South Korea and the multiple locations in northern Japan suggest that the current levels are higher.
This expansion has much in common with the expansion of the Qinghai (clade 2.2) strain three years ago at Qinghai Lake. Those sequences migrated north to Siberia and Mongolia over the summer, and then spread to Europe, the Middle East, and Africa. To date, all H5N1 west of China has been clade 2.2. Clade 2.2 also expanded into south Asia as well as South Korea / Japan in 2006/2007.
The current outbreaks represent the first reports of the Fujian strain (clade 2.3) in Japan, South Korea, or Russia. The movement into northern Japan signals movement into North America in the upcoming weeks via the East asian flyway. Similarly, the movement into Russia signals migration into northeastern Russia, which will also feed into North America. The H5N1 in South Korea signals movement into Siberia, where there will be mixing with clade 2.2 from Europe, the Middle East, and Africa. This will lead to more rapid evolution via recombination between clade 2.2 and clade 2.3.
All public human sequences from China have been the Fujian strain, and the clade 2.3.4 sequences from the public sequences from Japan and Russia are most closely related to sequences from a human case in Guangdong province in 2006. Thus, these clade 2.3 sequences have been confirmed in human cases in China and the soldier in South Korea was H5 positive, although Korea has denied the infection because of false negatives for N1.
This global expansion has been confirmed with Fujian sequences in three countries that have never reported Fujian sequences previously. Surveillance programs, especially those that focus on healthy wild birds have been abysmal, in part because cloacal swabs are collected, and the methodologies used have been fatally flawed.
Recent results in Japan have also highlighted problems linked to false negatives generated by the rapid tests, which have a notoriously low sensitivity. Testing of dead and dying whooper swans in Japan has been successful, including testing on samples that have previously been negative by rapid test.
A more serious surveillance effort is required to accurately map the transport and transmission of Fujian H5N1 by long range migratory birds. The prompt release of sequences by labs in Japan and Russia should serve as a model for this surveillance.
The reliance on false negatives and the hoarding of sequences remain hazardous to the world’s health.
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