People with chronic diseases, the obese, and pregnant women face a renewed threat of contracting deadly infection of A/H1N1 influenza as spring draws near.

Severe and fatal cases peaked in early and mid December last year, and have been dropping gradually since, but the disease threatened a resurgence as the weather warmed up, senior epidemilogists have warned.

"A new outbreak of A/H1N1 influenza is possible during this winter-spring season, and especially in the southern areas during summer," said Shu Yuelong, director of the Chinese National Influenza Center, which is affiliated with the Ministry of Health, at a meeting Thursday.

Cases of patients with chronic diseases, pregnant women and obese people were much more likely to become severe or even fatal.

Pathogenic studies showed a very small chance of the A/H1N1 virus mutating during this winter and spring, so vaccination was still essential to prevent potential outbreaks.

Analyses of past flu outbreaks showed a pandemic usually lasted more than two years before turning into seasonal flu, said Shu. "So the A/H1N1 influenza might be prevalent in the world for a considerably long time."

Experts said the government should promote vaccinations for high-risk groups, people in rural areas and migrant workers in urban areas.

According to the Chinese Center for Disease Control and Prevention, about 35,000 pregnant women and 37,000 children aged 6 months to 3 years had been inoculated with the A/H1N1 flu vaccine and no severe adverse reactions had been reported.

As of March 7, the Chinese mainland had reported a total of 127,427 cases of A/H1N1 flu, of which 8,320 were severe and 796 people had died.