Hong Kong wet markets battling health scare after outbreak of potentially dangerous bacterial infection linked to freshwater fish

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Hong Kong’s wet markets are grappling with a health scare after an outbreak of a potentially dangerous bacterial infection in the city was linked to freshwater fish sold by some vendors.

Medical experts have urged the public to avoid eating raw seafood after 79 cases of invasive Group B Streptococcus bacteria infection were detected in patients at public hospitals between September and October 10.

The Centre for Health Protection reported another nine cases on Thursday, bringing the total to 88.

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Lee Choi-wah, chairman of the Hong Kong Chamber of Seafood Merchants, said he feared businesses would be hurt, and called for sellers and shoppers to take precautions when handling fish. Cases have been linked to grass carp, bighead carp and snakehead fish.

Group B Streptococcus is a bacteria commonly seen in the intestinal, urinary and reproductive tracts. It is usually not harmful and does not lead to any symptoms, but potentially can cause infections in blood, bone, lungs or the protective membranes covering the brain and spinal cord.

The alarm was triggered this week when two people from a 32-strong cluster carrying a strain known as serotype III sequence type 283 (ST283) died.

As of Wednesday, 68 of the 88 patients had provided specimens for genetic sequencing analysis. Of the 68 cases, 32 involved ST283, while 27 belonged to other serotypes or another ST283 strain different from the cluster. The results for the remaining nine cases were pending.

Authorities have been keen to emphasise that some of the patients suffered from other illnesses and no evidence so far suggested the deaths were linked to the infection.

“People may just go to supermarkets instead of wet markets to shop for fish because they may think supermarkets have better hygiene standards,” Lee told a radio programme.

In Hong Kong, shoppers commonly choose raw fish by hand to check if the fish is of good quality and fresh. Freshwater fish is used mostly for congee, but it is often not cooked thoroughly to ensure tenderness.

The Centre for Health Protection said the strain carried in the 32 cases was almost identical in genetic sequencing to five fish or environmental samples taken from markets visited by some of the patients.

Half of the group had handled raw fish but no consumption was reported, the centre said. Two cases involved chefs working in different districts and one was a part-time fish seller.

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Some of those patients had visited Yeung Uk Road Market in Tsuen Wan, and a shop in Kai Tei in Yuen Long, which the Food and Environmental Hygiene Department has disinfected thoroughly. Authorities promised to take more samples from the fish wholesale market.

At the Tsuen Wan wet market, the department put up posters warning the public of the infectious disease on Thursday morning.

Joe Tan, 50, owner of Rong Kee Fresh Fish, told the Post his store was not among those involved in the cluster, but news of the outbreak had sent sales of grass carp down 20 per cent in the morning.

“We’re doing more cleaning work now,” Tan said.

A fishmonger waits for customers at a stall in Yeung Uk Road Market. Photo: K. Y. Cheng
A fishmonger waits for customers at a stall in Yeung Uk Road Market. Photo: K. Y. Cheng

At Loong Kee Fresh Fish stall, vendor Ms Lee said the business had been “affected a bit” by the virus scare over the past two days.

“We have sold fewer grey mullets,” she said.

Lee Choi-wah said most fishmongers wore gloves when handling fish or seafood, and advised consumers to pick a fresh fish by visually checking its skin or the colour of its eyeballs, but not to handle or even smell it.

A shopper in her seventies, who wished to remain anonymous, said she had bought a grass carp at Lee’s stall and had protected herself by wearing long sleeves, trousers and a pair of sports shoes.

“I asked the vendor to kill the fish, put it in the plastic bag, seal the bag and give it to me,” she said. “Before that, I won’t touch the fish at all.”

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Dr Wilson Lam, a specialist in infectious diseases, said the bacteria could be transmitted through direct contact or consumption.

He said consumers should avoid eating raw freshwater fish, and should make sure any seafood was properly cooked.

“Some people eat freshwater fish sashimi. But in Singapore, after they banned raw freshwater fish dishes, there was a significant drop of Group B Streptococcus cases during an outbreak [in 2015],” he said.

Lam also said if people really wanted to touch raw fish, they should wear gloves. If they cut themselves when handling it, and developed symptoms including a fever, they should seek medical help immediately.

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