Gene sequencing has confirmed the H9N2 virus recently isolated from a five-year-old boy is different from the two viruses isolated in 1999.

Acting Deputy Director of Health Dr Regina Ching said sequencing of internal genes had also been completed and showed that the virus genes were purely avian in origin.

Dr Ching said initial tests by HK University showed the virus was similar to the two virus strains found earlier this year through an on-going surveillance programme at poultry markets. H9N2 viruses are widely distributed in nature and commonly found in live birds.

"At this point, we do not see evidence of circulation of the H9N2 virus in the human population. Our sentinel influenza rates are stable and our laboratory does not have further potential H9 virus isolated," Dr Ching said.

She said further epidemiologic and virologic investigations will be needed to assess the significance of this finding and determine the child's source of infection.

"As a precautionary measure, members of the public, including poultry traders, should strictly observe personal and environmental hygiene."

Parents should not let their children touch live poultry and wild birds.