The nation's leading bird flu experts Sunday refuted a report that a new strain of bird flu had emerged in southern China, published by a foreign publication and widely cited by foreign media recently.

Scientists in Hong Kong and the United States said in a report released last week that a new strain of bird flu called the "Fujian-like virus," first isolated in the southern Chinese province of Fujian last year, had become prevalent in the Hong Kong Special Administrative Region, Laos, Malaysia, and Thailand.

Chen Hualan, director of the National Bird Flu Reference Laboratory at the Chinese Academy of Agricultural Sciences, rebuked the report, published in the US-based Proceedings of the National Academy of Sciences, saying its claims "lack scientific proof."

"The so-called 'Fujian-like virus' is not a new variant of the virus," she said "Gene sequence analysis of the virus shows that it shares high conformity with the H5N1 virus that was isolated in Hunan when bird flu broke out in early 2004."

Samples from every domestic bird flu outbreak are sent for isolation and gene sequence analysis at Chen's lab. Chen said that in 2005 and 2006, the lab had isolated some viruses in waterfowl in southern China which was reported to the Food and Agriculture Organization (FAO) and the World Organization for Animal Health (OIE).

"These viruses all remain steady in gene type and there is no marked change in their biological characteristics," she said.

Chen said there was only one new variant of the virus, which was isolated in North China's Shanxi Province and the Ningxia Hui Autonomous Region at the beginning of this year and has been reported to FAO and OIE.

Experimental results show that the variant is weak in triggering disease in mammals and a new vaccine, which has been put into use in these areas, has effectively brought it under control.

Chen also defended the effectiveness of China's bird flu vaccine, saying that it had a "good effect," in response to the report's surmise that the current vaccine was less effective for the "Fujian-like virus."

The report claimed that through the analysis of serum samples from 76 chickens for signs of antibodies against three H5N1 variants, including the Fujian-like strain, they found almost all of the samples displayed two to four times more antibodies to the other two variants than to the Fujian virus, suggesting that the vaccine given to the chickens was less effective against that strain.

Chen said that the evaluation of the vaccine was "not scientific" as where the chickens were from and whether they had been vaccinated were unknown.

Statistics from the Ministry of Agriculture showed that more than 95 per cent of domestic poultry had been vaccinated between January and October.

Shu Yuelong, director of the National Influenza Centre at the Chinese Centre for Disease Control and Prevention, also refuted the report's allegation that five people in southern China were actually infected by the new "Fujian-like virus."

Shu said that altogether 16 variants of bird flu viruses have been found in the 20 confirmed cases of human infections on the Chinese mainland since October 2005 seven in 2005 and 13 in 2006. "Fifteen out of the 16 variants were isolated from cases in southern China and they belong to the same gene type," Shu said. "There is no proof that five of them were infected by a new mutated virus."