Group B Streptococcal Infection/Freshwater Fish


There were recent cases of Group B streptococcal infection in Hong Kong. The victims included fishmongers, restaurant cooks and the public. Subsequent investigations revealed that some of them had been exposed to freshwater fish before the onset of symptoms. With quite many cases of Group B streptococcal infection in a short period of time, what precautions should be taken by the public?


What is Group B Streptococcus?

Group B Streptococcus (GBS) is a bacterium commonly found in the gastrointestinal tract and reproductive system of humans. It normally causes no harm to its carriers except for possibly developing sepsis, meningitis and pneumonia in persons with weak immunity due to chronic diseases. Pregnant women may also transmit GBS to the newborn babies during pregnancy and childbirth, leading to GBS infection in the newborn. The first record of GBS infection through food consumption occurred in Singapore in 2015, which was caused by the serotype III sequence type 283 (ST283), an extremely rare strain of GBS. After epidemiological investigation of the GBS infection, it was found that the case was strongly associated with unprocessed freshwater fish.


Currently, there is a lack of reliable data available for research on GBS/GBS ST283 strain in the aquaculture, supply chain and retail sale of freshwater fish. The mechanism of their infection resulting in foodborne disease is still unclear. But, it is certain that GBS/GBS ST283 strain is not heat-resistant, which means we can prevent contracting GBS by thoroughly heating.


How to prevent GBS infection?

The Municipal Affairs Bureau (IAM) reminds the public to pay attention to personal, food and environmental hygiene, and take the following essential precautions:

  1. Always keep hands clean, especially before eating and after going to the toilet;
  2. Avoid eating raw seafood, especially freshwater fish;
  3. While shopping in a wet market, never pick up fish with bare hands, and avoid direct contact with the wastewater and waste matters in the wet market;
  4. Wear protective gloves when handling seafood and do not touch it with bare hands. When there are wounds on the hands, dress them properly before putting on the gloves;
  5. Always separate raw and cooked foods, and use different sets of knives, cutting boards and containers to handle and hold raw and cooked foods separately to avoid cross-contamination;
  6. After cooking, clean the kitchen and utensils thoroughly, and dispose of the garbage properly. 

Lastly, fishmongers and people engaged in the food industry have to be vigilant and avoid touching raw fish with bare hands.


Source: FAO. 2021. Risk profile - Group B Streptococcus (GBS) – Streptococcus agalactiae sequence type (ST) 283 in freshwater fish.