A 59-year-old local woman was found to have contracted H5N1 avian flu virus after visiting the mainland last month, Hong Kong Secretary for Food and Health York Chow said Wednesday.

Speaking at a press briefing Wednesday evening, Chow said the patient went to the mainland on Oct. 23 where she visited places including Shanghai, Hangzhou and Nanjing. She developed flu symptoms such as cough and fever on Nov. 2, one day after returning to Hong Kong, and was later admitted to Tun Mun Hospital.

Chow said since the patient, who is now in a serious condition, had been to wet markets in the mainland, he believed that the contraction was probably happened outside Hong Kong. But he did not rule out the possibility that it was a local case.

The Serious Response Level under the government's Preparedness Plan for Influenza Pandemic is activated, said the city's health chief, adding that the government will submit the case to the World Health Organization and various departments will call on a conference on Nov. 18.

There was an outbreak of the disease in 1997 in Hong Kong in which six people died. About 1.5 million poultry were killed to prevent further spread of the disease.