A 68-year-old woman is in critical condition in Tuen Mun Hospital with the H7N9 strain of bird flu. It is the first confirmed case of bird flu in the city this winter. The woman was admitted to the hospital on Christmas Day with fever and pneumonia and was isolated in intensive care, Secretary for Food and Health Dr Ko Wing-man said yesterday. The woman had visited the Longgang district of Shenzhen on December 13 with two female friends and they had eaten chicken there, Ko said, adding that the woman had not touched any live poultry or visited a wet market either in Longgang or Hong Kong before she developed symptoms. Ko said health authorities were still trying to determine the source of the virus. The five women who shared a ward with the patient when she was first admitted to hospital had also been isolated and authorities were trying to track down the woman's friends who dined with her in Longgang, as well as her nine family members, Ko said. He said the government had raised Hong Kong's influenza pandemic response level to "serious", meaning public hospitals would limit visiting times and strengthen protection controls. Sales of local and imported live poultry would not be affected. "H7N9 cases have been moving south," Ko said. "We expect to see more imported H7N9 cases." He advised Hongkongers to stay away from live poultry, especially when visiting areas where there had been bird-flu cases. The case comes after mainland authorities on December 7 reported that a 66-year-old man had died of H7N9 in Meizhou , Guangdong, four days earlier, the first confirmed H7N9 death in the province this winter.