The Centre for Health Protection is investigating a case of influenza-A virus (H9N2) involving a two-month old girl who lives in Shenzhen. The Hong Kong-born baby is stable in Tuen Mun Hospital.

Centre controller Dr Thomas Tsang today said the girl was admitted December 22 with a runny nose, vomiting and a cough but no fever. She was discharged the next day and returned to Shenzhen. But she lost her appetite later and was sent to a local doctor for treatment. As her white blood cell count was high, her mother brought her back to the hospital December 29.

Test results found the presence of H9N2, which is a mild form of avian flu. Guangdong health authorities have been informed of the case.

The Department of Health will also inform the World Health Organisation, the Mainland's Ministry of Health, and health authorities of Macau.

"The investigation is ongoing and we want to find the source of the virus," he said. "We are particularly concerned about whether the case is human-to-human transmitted and whether there are other people infected."

Dr Tsang said the virus is widely spread among birds and poultry in southern China. There were four human cases in the past 10 years and all patients recovered.

He said one of the major causes of H9N2 is close contact with live poultry and birds.

"The rest of the girl's immediate family is asymptomatic. We are monitoring their condition and have given them Temiflu," Dr Tsang said. "Since the girl's white blood cell count is high the hospital is finding out whether she has other blood disorders, such as leukaemia."