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, said the Ministry of Health (MOH) 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," the MOH spokesman Mao Qun'an said.

"But the mutation is impossible to 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 found in Europe so far.

The major channels of human infection involve direct contact with infected poultry or their secretion and excretion, as well as inhalation of the particles of the virus from the poultry's secretion and excretion, said Mao, noting that the general public won't get infected if they keep themselves away from sick and dead poultry.

By Nov. 25, the World Health Organization (WHO) had reported 132 laboratory-confirmed human cases of bird flu including 68 deaths.

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