The potential problem of underreporting might not only be technical. There are also many a claims that Chinese medical personnel have been arrested for trying to report cases. China imposed serious restrictions on the investigation and reporting of suspected cases of bird flu in June 2005.

Opinion of Virologists

Virologists consider the relative absence of human cases of bird flu in China strange, given its widespread infection in birds. China has reported 22 poultry eruption in 10 provinces all across the country since mid-October 2005, the latest being on Friday.

The WHO told the official Chinese news agency Xinhua last week that the virus that caused the eruption in Hunan is the same as the H5N1 flu in Vietnam and Thailand, where it has caused 113 confirmed human cases and 55 deaths so far. Officials said five people suspected of having the virus had died, in addition to a six-year old boy who became the first confirmed casualty.

Reports of World Health Organization

The World Health Organization said the flu's rapid expand posed a potential threat for a serious human outbreak. However, there has been still been no signal of it jumping from human to human. A WHO spokesman told the BBC that it was becoming clear that injure had been around in the region much longer than first thought.

That it had multiplied the risk of human infections, and of the virus mutating, perhaps by attaching itself to human flu and becoming far more deadly. The WHO believes the disease is now too serious for individual countries to deal with alone. Among the Thai dead were two women and three men, according to a statement subjected by Thailand's disease control director Charal Trinvuthipong.

More reports on deaths caused by the bird flu

Earlier on Monday, the Thai Agriculture Ministry said the virus had been detected in eight more provinces, in addition to two provinces previously confirmed. It said all the victims were from two provinces central Sukhothai and Chachanoengsao, east of the capital Bangkok.

The Thai outburst has triggered alarm across the region. In Laos, where thousands of chickens have died, corpses of dead birds have been sent to Vietnam for tests. There are also reports of a boy dying of bird flu in the adjacent Cambodia, the BBC's Rachel Harvey reports.