Fourth infection may have come from Tseung Kwan O market A nine-month-old girl who made frequent visits to a wet market has been confirmed to have contracted H9N2, a rare form of bird flu, bringing the total number of infections recorded in Hong Kong to four. Controller of the Centre for Health Protection, Thomas Tsang Ho-fai, said this was the third time H9N2 viruses had been found in humans in the city. Two girls, aged one and four, were infected in 1999 and in 2003 a boy was infected. They all recovered. 'Further genetic sequencing is being conducted to see if it is different from the previous strain and determine if the virus is completely of avian origin. We expect to have tests results soon,' Dr Tsang said. 'This is an isolated case and the source of infection is being investigated. Initially it seems that the latest case is similar to the ones previously reported.' The centre said it would inform the World Health Organisation, the Ministry of Health in Beijing and the health authorities in Macau and Guangdong province about the latest findings. The baby, who lives in Tseung Kwan O with her parents and grandmother, is being monitored in isolation at Princess Margaret Hospital. She developed symptoms of an upper respiratory tract infection and fever on March 4 and was admitted to United Christian Hospital two days later. The baby was discharged on March 9 and a laboratory test yesterday confirmed that she had contracted H9N2. 'The concerned family told us the baby was a frequent visitor to King Lam wet market. She was taken to the market almost every day for a week before she fell sick,' Dr Tsang said. He said the family had bought a chicken from Hau Tak wet market on February 16, but the baby did not go to the market that day. 'We will look into histories of bird and poultry exposure and visits to places with birds and animals as we conduct the investigation.' Officers from the Food and Environmental Hygiene Department collected samples from the wet markets for tests, and samples were taken from the baby's home. A spokeswoman for the department said it would help stallowners at the two wet markets clean and sterilise their sites. Dr Tsang, however, dismissed fears that Tseung Kwan O residents were at a high risk. He said H9N2 viruses were often found in live poultry. 'The viruses naturally are present in them. But H9N2 rarely infects humans,' he said. The Hospital Authority said public hospitals would step up the surveillance of cases with flu-like symptoms. Infectious diseases expert Lo Wing-lok warned parents not to take children under 12 to wet markets. 'Younger children's immune systems are weaker,' Dr Lo said. Children were also shorter, which meant they might have closer contact with cages. 'When chickens move their wings, small particles that carry the virus carry into the air. Children could be infected when inhaling these particles.' Mr Cheung, an owner of a poultry stall at King Lam wet market, said the market should not necessarily be blamed. 'The case might not have been caused by us. We could be innocent.' He said he washed his stall twice a day but would step up cleaning.