The Centre for Health Protection is investigating a suspected imported human case of avian influenza A(H7) involving a 10-year-old boy who travelled to Guangdong.
He visited Foshan with his family from December 31 to January 3.
He fell ill on January 8 and was admitted to Princess Margaret Hospital the following day.
He was discharged but later readmitted for isolation.
He preliminarily tested positive for H7.
His close contacts are asymptomatic and are under medical surveillance.
The centre urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.