A sample collected from a market in Hong Kong has tested positive for bird flu H9, days after a two-year-old boy who visited the venue contracted a mild strain of the infectious disease. But the Centre for Health Protection (CHP) said on Monday that the risk of a serious bird flu outbreak was low. The boy, who lives in Sha Tin, became ill after visiting Wo Che Market in the district and was later confirmed to be infected with H9N2 avian influenza, the centre said.