Genetic analyses by CVI of the highly pathogenic avian influenza A(H5N8) virus that infected several poultry farms in the Netherlands in November 2014, showed a close relation to H5N8 strains earlier found in South Korea and Japan. Sequence data suggest that the virus was probably carried to the Netherlands by migratory wild birds from Asia, possibly through overlapping flyways and common breeding sites in Siberia.
The highly pathogenic avian influenza H5N8 virus probably originated in China, where it was isolated in 2009–2010. Pathogenicity studies showed that the virus was highly virulent in chickens but mildly or moderately virulent in wild ducks. Phylogenetic research demonstrated that it was the product of various reassortment events. The RNA of the virus consists of segments that come from other influenza viruses and of parts of the highly pathogenic H5N1 virus that has circulated in China since 1997 and has spread worldwide since 2004.
Beginning in January 2014, H5N8 virus spread rapidly in South Korea, initially mainly among farmed ducks. During the first outbreaks among farmed ducks, numerous dead Baikal teals were found near the affected farms, leading to the hypothesis that infection was carried by the wild ducks. Genetic analysis of the virus indicated that isolates from infected domesticated ducks and dead Baikal teals in the surrounding area in South Korea strongly resembled earlier isolates from China. Recent phylogenetic studies of H5H8 viruses isolated from infected poultry and wild birds in 2014 in South Korea indicate that migrating birds have played a key role in the introduction and spread of the virus in the initial phase of the 2014 outbreak.
In mid-April 2014, the presence of highly pathogenic H5N8 virus was demonstrated at a poultry farm in Japan after a rise in the death rate was noted. During a monitoring program in November 2014, fecal samples of migrating Tundra swans tested positive for the H5N8 virus. A H5N8 virus was isolated from a Eurasian wigeon in Northeast Russia in September 2014. In regard to time, this location in Siberia fits well with the hypothesized route of H5N8 virus introduction into Europe.
(online ahead of press Emerging Infectious Diseases, May 2015:)
Bouwstra R, Heutink R, Bossers A, Harders F, Koch G, Elbers A. Full-genome sequence of influenza A(H5N8) virus in poultry linked to sequences of strains from Asia, the Netherlands, 2014. Emerg Infect Dis. 2015.
In this publication also peer reviewed article on H5N8 in England and Germany will be published:
- Hanna A, Banks J, Marston DA, Ellis RJ, Brookes SM, Brown IH. Genetic characterization of highly pathogenic avian influenza (H5N8) virus from domestic ducks, England, November 2014. Emerg Infect Dis. 2015;
- Harder T, Maurer-Stroh S, Pohlmann A, Starick E, Höreth-Böntgen D, Albrecht A, et al. Influenza A(H5N8) virus similar to strain in Korea causing highly pathogenic avian influenza in Germany. Emerg Infect Dis. 2015.