The Centre for Health Protection said an analysis showed that among the 79 patients who tested positive for the pathogen, invasive Group B Streptococcus, 32 had the same source of infection.
They are aged between 31 and 87.
Half of them – including two restaurant cooks and a part-time fish seller – said they had handled freshwater fish.
Environmental and fish samples collected from the markets some of the patients visited also tested positive for the pathogen with the same genetic sequence.
The vice-president of the Hong Kong Society for Infectious Disease, Wilson Lam, told an RTHK programme the outbreak is concerning.
He said people should wear gloves when handling fish.
“People should be cautious. If they develop symptoms such as inflammation and fever after handling freshwater fish, they should see a doctor quickly,” he said.
Speaking on the same programme, the chairman of Hong Kong Chamber of Seafood Merchants, Lee Choi-wah, said it’s unnecessary for people to touch the fish when shopping at markets, as they can judge whether a fish is fresh from its appearance.