Genetic mutation had been detected in eight A/H1N1 flu cases on the Chinese mainland, an official with the Chinese National Influenza Center said Wednesday.

Shu Yuelong, director of the center, which is affiliated with the Ministry of Health, said in an interview that the mutated virus was not resistant to drugs and could be prevented by vaccines.

According to Shu, the first mutated strain of the A/H1N1 flu was discovered in June this year in an imported case from Britain. Similar strain was detected three months later in Zhejiang Province.

The health department of Hong Kong Special Administrative Region (SAR) announced one human swine influenza (HSI) virus which had the same mutation as the one detected in Norway recently.

According to the World Health Organization (WHO), same mutation had been found in other countries including Brazil, Japan, Mexico, Ukraine and the United States.

"Mutations were almost inevitable in influenza viruses," Shu said.

Shu said the mutation detected recently was isolated and the cases were not interrelated to each other.

"This kind of mutant virus has been found in patients with slight and heavy symptoms as well as those who have recovered. The virus has not widely spread so far," said Yu Hongjie, an expert from the Chinese Center for Disease Control and Prevention.

The WHO concluded that the mutation' s affection to the public health had not been clear but it reminded health workers to strengthen the monitoring of the flu virus, Yu added.

"As far as we know, the vaccines are still effective in the prevention of this kind of mutant virus." said Chen Weiyun, spokeswoman for the WHO Representative Office in China.

Chen said the WHO had not decided to shift its focus from battling the flu to combating its virus mutations.

If the study revealed that mutations would be a threat, the WHO would advise the governments of all countries to adjust their measures.