The government has banned imports and the sale of live chickens for three weeks after an infected chicken carcass was found at a wholesale market on Tuesday.
It has also raised the city’s flu alert system to “serious”.
Two wild birds were also found to have died of the the virus.
The government said it was tracing the source of the chicken carcass, but it was not clear whether the chicken came from a local farm or was imported.
Hong Kong is quick to take action against infectious diseases after an outbreak of the deadly respiratory disease SARS in 2003 killed 300 people in the city and a further 500 worldwide.
In 2009, 300 people were placed under quarantine at a Hong Kong hotel after a guest contracted swine flu