A Chinese health expert has warned of a possible flu outbreak this winter as new variants of the virus emerge.

"There is no current sign indicating a pandemic outbreak of influenza, but it's still too early to make clear predictions," said Guo Yuanji, director of the anti-flu expert team with the Health Ministry, at a workshop held in Nanjing, capital of east China's Jiangsu Province, from July 11 to 14.

"The answer lies with the influenza A-3 virus. Once it develops into a new variant, flu outbreaks are likely to happen," Guo said.

Cases of the influenza A-3 virus rose sharply in early 2003. And a nationwide medical survey from that year showed most people examined had the antibody of the virus, which would last for one to two years.

Generally, when 70 percent of a population had an antibody, it is possible the virus will mutate, Guo explained.

Future surveillance should be focused on virus mutation in south China and the possible areas where a flu pandemic may originate in winter, Guo said. But he warned that current medical detection technologies still lag behind the development of new viruses.

The last flu pandemic took place 30 years ago, and another peak outbreak of flu will come sooner or later according to the general rule in epidemiology, he said.