Jun 10, 2005 (CIDRAP News) – The deadly H5N1 avian influenza virus is behaving in new and unpredictable ways, a World Health Organization (WHO) spokesman said today.

Shigeru Omi, WHO regional director for the Western Pacific, spoke today in Beijing, according to news service reports. China this week announced an outbreak of H5N1 among domestic geese in a far northwestern province. An earlier outbreak in May killed more than 1,000 migratory birds in China.

The virus appears to be more pathogenic in birds in China than elsewhere, Omi said. Conversely, it appears to have become more transmissible to humans in Vietnam, but less pathogenic.

"All of this shows the virus remains unstable, unpredictable and very versatile," Reuters quoted Omi as saying. "It may have new and unpleasant surprises in store for all of us."

Media reports since late May indicate that people continue to contract avian flu in Vietnam, although the scant details and sometimes unclear reports make it difficult to determine how many people have fallen ill in recent weeks.

"The outbreak has slowed recently," Trinh Quan Huan, head of the Health Ministry's Preventive Medicine Department, said in a Reuters quote attributed to a Vietnamese online service.

China has not reported any human cases of H5N1, and officials there said the domestic poultry outbreak had been brought under control through culling, quarantine, and vaccination, Reuters said.

However, Reuters cites a report by the official Xinhua Chinese news agency that said 17,014 birds were slaughtered in the affected area of Xinjiang Province, Tacheng City. China's report to the World Organization for Animal Health (OIE) on June 8 said only 13,457 birds had been destroyed in the domestic outbreak.

Omi urged heightened vigilance around the avian flu virus, emphasizing that countries must share information, research, and virus samples with international agencies, according to an Associated Press (AP) story today.

The WHO is looking forward to getting samples from China's outbreaks because "sharing samples is very critical," Omi said. In addition, WHO officials are awaiting Beijing's permission to travel with Chinese authorities to Qinghai province, the scene of the migratory bird deaths.

Gao Qiang, China's health minister, was quoted by the AP as telling reporters in Hong Kong that WHO teams would be able to visit infected areas.