Studies show the H5N1 strain of virus separated from China's human cases of bird flu has mutated compared with the strain found in Vietnam's human cases, the Ministry of Health (MOH) said on Monday.

Lab tests find the H5N1 strain of virus separated from recent human cases is highly homologous with that found in poultry samples from the bird flu outbreak places, according to the information office of the MOH.

However, compared with the virus strain from the human cases in Vietnam, the genetic order of H5N1 in China's human cases has mutated "to a certain degree," MOH spokesman Mao Qun'an said.

"But the mutation doesn't necessarily cause human-to-human transmission of the avian flu," he noted.

Mao said since the H5N1 bird flu first broke out in 1997, most human cases have been reported in Hong Kong, Thailand, Vietnam, Cambodia, Indonesia and the Chinese mainland. No human case has been reported in Europe to date.

The major channels of human infection involve direct contact with infected poultry or their secretions and excrement, as well as inhalation of virus particles of the virus from poultry secretions and excrement, said Mao, noting that infections are rare as long as people stay away from sick or dead infected poultry.

As of November 25, the World Health Organization (WHO) had reported 132 confirmed human cases of bird flu including 68 deaths.

China has reported three confirmed human cases of bird flu, including two fatalities from east China's Anhui Province and one case from central China's Hunan Province where the patient recovered.

(Xinhua News Agency November 29, 2005)