The researchers identified the management of freshwater fish as the key risk factor in an epidemic in Hong Kong.
Invasive infection of group B Streptococcus (GBS) caused by type 283 sequence (ST283) has also been linked to the consumption of crusted freshwater fish. At the end of the summer of 2024, surveillance in Hong Kong detected an increase in cases.
A case-control study has been carried out involving all patients with SGB invasive reported in August 2024. Cases were defined as patients infected with St283 strain, while witnesses had non-ST283 strains. The results were published in the Epidemiology and infection journal.
Among 170 patients with invasive SGBs, 131 were identified as cases and 39 as witnesses. The physical handling of crus water fish was the strongest risk factor for ST283 infection.
Past incidents highlight the risk
Scientists carried out an environmental sampling on four of the wet retail markets visited by the ST283 cases, a wholesaler and three local pool farms.
In 2015, Singapore recorded a large epidemic of food involving more than 100 cases of Invasive ST283 infection. Epidemiological surveys indicated an association with the consumption of crude freshwater fish. Cases of ST283 invasive GBS have been continuously reported in Southeast Asia and around Southeast Asia.
In September 2021, Hong Kong experienced an increase in the invasive cases of the GBS allocated to the St283 strain. The epidemiological surveys carried out by the Center for Health Protection (CHP) have suggested handling crude fresh water fish and eating freshwater fish insufficiently cooked as possible risk factors.
In the 2024 epidemic, 61 of the 131 cases were men and 70 women, with ages from 29 to 97 years old. The start dates varied from August 8 to September 8, 2024. Clinical presentations mainly involved sepsis, joint abscesses and meningitis. Four people died.
Role of public awareness
The freshwater fish involved included a variety of species, the grass carp being the most common. These fish have been purchased in more than 50 markets in all districts, excluding a single common source.
Only four cases and a control declared consuming insufficiently cooked freshwater fish. No cases concerned professional fish managers, such as fishmongers, which are equipped with protective equipment such as gloves and have relevant knowledge and skills.
Two samples of freshwater fish and three environmental swabs from a freshwater retail sale in a wet market tested positive for ST283.
Government services have carried out cleaning and disinfection on the relevant markets and inspected all fish stands, fresh provision stores authorized and authorized the premises selling freshwater fish in Hong Kong. They offered hygiene education to operators, advising them to do a deep cleaning and disinfection after opening hours.
Awareness of the public to preventive measures should include not eating raw water fish or subcuire and also wear appropriate protective equipment and practice good hand hygiene when entering into contact with such fish.
Scientists have said that the study represents the first epidemiological evidence specifically linking physical contact with crude freshwater fish at an increased risk of invasive infection of the GBS ST283.
“The results underline the need for sustainable preventive strategies targeting high -risk fish processing practices, especially during hot periods promoting the environmental proliferation of ST283. This knowledge will allow the development of preventive and more targeted control strategies, including precise health education messages”, according to researchers.
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