Recombinomics: FAO Warns of Fujian H5N1 Spread In China and Vietnam

Recombinomics Commentary 14:20
August 29, 2011

At the same time, 2008 marked the beginning of renewed geographic expansion of the H5N1 virus both in poultry and wild birds.

The advance appears to be associated with migratory bird movements, according to FAO Chief Veterinary Officer Juan Lubroth. He said migrations help the virus travel over long distances, so that H5N1 has in the past 24 months shown up in poultry or wild birds in countries that had been virus-free for several years.

"Wild birds may introduce the virus, but peoples' actions in poultry production and marketing spread it," Lubroth noted.

Recently affected areas are to be found in Israel and the Palestinian Territories, Bulgaria, Romania, Nepal and Mongolia.

A further cause for concern, Lubroth said, is the appearance in China and Viet Nam of a variant virus apparently able to sidestep the defences provided by existing vaccines.

In Viet Nam, which suspended its springtime poultry vaccination campaign this year, most of the northern and central parts of the country -- where H5N1 is endemic -- have been invaded by the new virus strain, known as H5N1 - 2.3.2.1.

The above comments are in an FAO announcement warning of the spread of Fujian clade 2.3 (sub-clade 2.3.2.1), which was reported in the spring of 2008 in outbreaks in poultry in South Korea and Russia, as well as whooper swans in northern Japan. The sub-clade has a clade 2.3.2 HA reassorted with other genes from clade 2.3.4. This sub-clade was reported earlier in Hong Kong, and the spread to northern Japan, Korea and Russia raised concerns that it would migrate to Mongolia in the summer of 2008.

Sequences analysis confirmed this migration, and identified recombinants between clade 2.2.1 in Egypt and clade 2.3.2 in wild birds. Clade 2.3.2 was subsequently confirmed in poultry in Romania and a wild bird in Bulgaria.

The most recent public sequences are from a Feb 2011 isolate from a chicken in Vietnam, but this HA sequence is related to a 2010 human case in China (A/Hubei/01/2010). WHO has published an HA phylogenetic analysis, which includes the Hubei sequence, as well as poultry sequences from Vietnam. The is no current H5N1 vaccine against human clade 2.3.2 sequences, although the Hubei sequence has been selected as a candidate.

Full sequences for all 8 gene segments of the Hubei isolate are available at GISAID, and these sequences confirm matches with wild bird sequences from 2008.

Release of 2011 human sequences from China and southeast Asia would be useful.