The Centre for Health Protection has confirmed an imported human case of avian influenza A(H7N9) involving a 10-year-old boy who travelled to Guangdong.
It is the fourth human H7N9 case in Hong Kong this winter.
Contact tracing has identified 27 close contacts and 70 other contacts.
Four healthcare workers have mild symptoms. Two of them have tested negative for influenza A so far. The others have remained asymptomatic.
From 2013 to date, there have been 20 imported human H7N9 cases in Hong Kong, involving 13 males and seven females aged from five months to 85 years, with seven deaths.
The centre urges the public to maintain strict personal, food and environmental hygiene both locally and during travel.