Health Secretary Lo Chung-mau on Saturday warned people not to touch freshwater fish with their bare hands, after an outbreak of a deadly infection linked to fish.

The Centre for Health Protection said 27 cases of Group B Streptococcus had been reported over the past couple of weeks, two of which proved fatal.

It said the strain involved – ST283 – is commonly found in freshwater fish, especially farmed fish in Southeast Asia.

Speaking to reporters at an event, Lo said the bacteria is highly invasive and pathogenic.

"Our tracking shows that the bacteria may be found in freshwater fish across all 18 districts of Hong Kong. We're not telling people not to eat freshwater fish, but to be careful when handling them, including not touching them with bare hands," he said.

"You should only eat cooked freshwater fish. Do not eat uncooked or even raw ones, which can be dangerous."

Separately, the health chief said a taskforce has been set up to look into a blunder involving a medical device that failed to produce X-ray images during a procedure at Queen Elizabeth Hospital, leaving a 66-year-old patient fighting for his life.

Lo said preliminary investigation found that the X-ray imaging machine might have had problems emitting energy during the procedure, adding that the taskforce will also examine whether there were any issues with the doctors, nurses, and X-ray technicians involved.

The patient is in a high dependency unit in a critical condition.