WHO, OIE downplay importance of new H5N1 variant

Robert Roos News Editor

Aug 31, 2011 (CIDRAP News) – The World Health Organization (WHO) and the World Organization for Animal Health (OIE) took pains today to downplay the significance of a new H5N1 avian influenza variant that another major international organization warned about this week.

In an Aug 29 statement, the United Nations Food and Agriculture Organization (FAO) said a new H5N1 strain called clade 2.3.2.1 had emerged recently in Vietnam and China and that existing poultry vaccines were ineffective against it. The statement also cited recent increases in H5N1 bird outbreaks and warned about a possible major resurgence of the virus.

The WHO said today that its Global Influenza Surveillance and Response System recognized the H5N1 variant in February. "Based on available information, this evolution of the H5N1 virus poses no increased risk to public health," the WHO statement said. "It is not considered unusual because influenza viruses are constantly evolving, especially in areas where they circulate regularly in poultry."

The agency further said clade 2.3.2.1 does not change the public health implications of H5N1 viruses, given the available information. "Human cases of H5N1 infection remain rare and sporadic events, occurring mostly in areas where H5N1 viruses circulate regularly in poultry," the statement said.

The OIE made similar points in a statement today. It said the emergence of clade 2.3.2.1 is a result of minor genetic changes that typify the natural evolution of the virus.

"This is not immediate cause for alert but, as with the emergence of any new strain, reinforces the need for sustained monitoring of viruses in animal populations so that changes in viruses circulating in the field are detected at an earliest stage and that most appropriate disease control strategies are chosen to best protect animal and public health, the OIE said.

The agency also commented that avian flu vaccines, like human flu vaccines, need to be tested regularly to see if they are effective against the viruses in circulation. The OIE reference laboratory in Harbin, China, has developed a vaccine that, in trials, has protected poultry from clade 2.3.2.1, the statement said. Once available for field use, the vaccine will be employed in countries where the new variant has been identified.

"Registration and manufacturing of a poultry vaccine with the new seed strain is in progress," the OIE said.

Meanwhile, a clade 2.3.2.1 virus caused the illness of a 59-year-old Hong Kong woman who contracted an H5N1 infection last November, probably while traveling in mainland China, according to a report today by The Standard, a Hong Kong newspaper. The story cited Hong Kong's Centre for Health Protection (CHP) as the source of the information.

Hong Kong health officials said at the time that the virus in the woman's case belonged to clade 2.3.2. She recovered from her illness, according to online information from the CHP.