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Rapid Evolution of H5N1 Wild Bird Flu in Europe and Asia
December 24, 2005
Since the last issue of AIDEnews, outbreaks were suspected or confirmed in Omsk, Tambov, Cheliabinsk, Altai, Kurgan Regions in November, and in Kurgan, Astrakhan and Kalmykia Regions in December. In Astrakhan Regions (in the Volga Delta near the border with Kazakhstan) and in Kalmykia, around 600 dead swans have been found.
Research undertaken by the Russian Vektor Center's zoonotic infections laboratory indicated differences between viruses isolated in Novosibirsk Region: virus isolated in the summer/autumn of 2005 is almost identical to the strain that caused an outbreak in northern China in spring 2005 but the virus found in the second outbreak was similar to virus found in Viet Nam in 2002-2003
The above comments indicate that there are now at least three versions of HPAI H5N1 circulating in Europe. The most common version is closely related to the bar headed geese isolates from Qinghai Lake. These isolates have an HA cleavage site sequence of GERRRKKR which has been reported for isolates in Romania, Turkey, Croatia, Ukraine, and Russia (Tula). This cleavage site matches earlier isolates from Novosibirsk, Mongolia, and Kazakhstan and has been associated with wild bird flu sequences.
The latest Ukraine OIE report however, describes isolates that have a genetic background similar to the above wild bird flu isolates, but with a cleave site of RERRRKKR, which matches the most common cleavage site in Asia including the original Guangdong goose sequence from 1996.
The comments above indicate a third H5N1 species related to isolates from Vietnam in 2002-2003 has been detected in the Volga Delta region. The earlier Vietnam isolates (A/Chicken/Vietnam/Ncvd8/2003(H5N1) , A/DuckVietnam/Ncvd1/2002(H5N1)) were also HPAI, but had a unique HA cleavage site, REIRRKKR, which had also been detected in a teal from China (A/teal/China/2978.1/2002(H5N1)) as well as swine from Fujian province (A/swine/Fujian/F1/2001(H5N1), A/swine/Fujian/F1/2003(H5N1)) isolated in 2001-2003. Russia has not filed an OIE report of the outbreaks in the Volga Delta / Kalmykia regions, so it is unclear if those isolates have the REIRRKKR or RERRRKKR cleavage site, but clearly the HPAI H5N1 in Europe is becoming more diverse.
This diversity highlights the need for more surveillance of wild birds in Europe, the Middle East, and Africa because the introduction of HPAI H5N1 into these regions presents new opportunities for recombination and the generation of novel genes which may have an increased efficiency of human-to-human transmission.
Recent reports from the Ukraine indicated the H5N1 isolated on the Crimea peninsula was unique and birds died 2-8 hours after symptoms, which included blindness in waterfowl. These novel isolates also point toward the need from more sequence data from poultry outbreaks in China. Novel HA cleavage sites have been reported in whooper swan isolates from Mongolia as well as a chicken in Hunan, which was linked to the first reported human H5N1 case in mainland China.
H5N1 is clearly rapidly evolving in Asia and Europe and timely reporting of sequence data is increasingly important.