HONG KONG - Hong Kong health authority said on Saturday that a two-year-old boy has been confirmed with H5N1 Influenza A and urged the public not to panic.

The Center for Health Protection said the boy's condition has changed from stable to serious after testing positive for the deadly avian influenza, while his parents' tests for influenza were negative.

"The boy's parents are all along asymptomatic, which means that the chance of a human-to-human transmission is slim," said a spokesman of the center in a statement.

The boy was put to intensive care treatment while his parents were in quarantine in the same hospital.

A native of China's southern city of Guangzhou, the boy went to Hong Kong with his family on May 26 to seek medical treatment after running a fever for weeks.

After reporting the influenza case, the city government raised its bird flu alert level to "serious" and tightened control on live chickens imports, and strengthened supervision of local farms and markets.

The authority has intensified disease monitoring and infection control in public hospitals. Hospital staff will keep close watch over visiting patients and enforce triage assessment and appropriate segregation at waiting areas in line with clinical guidelines.

Besides, all 30 local chicken farms will be inspected within two days to ensure that their chickens are healthy and biosecurity and health measures are followed strictly.

The Center for Food Safety has contacted with its mainland counterparts in search of the infection source. Once the source is located, an area within 13 km radius will be declared an import control zone. Imports of live poultry and poultry products will be suspended for 21 days in the zone.

"At the moment, it is an isolated case. We feel that there is no need for panic among Hong Kong citizens," said York Chow, the Secretary for Food and Health of the city government, while addressing media earlier in the day.