SINGAPORE - Food stalls will no longer be allowed to sell Chinese-style raw fish dishes - including raw fish porridge - unless they can show that the fish is from safe suppliers, the authorities said on Friday (Nov 27).
This comes as they confirm that there is "an association" between eating Chinese-style raw fish dishes and what appears to be an aggressive strain of Group B Streptococcus (GBS) bacteria.
This strain - GBS Sequence Type (ST) 283 - has caused serious infections in several people who had eaten raw fish dishes this year, but it had not been clear until now that there is a definite link.
A joint government statement on Friday said that a Ministry of Health investigation "established an association between the consumption of Chinese-style ready-to-eat raw fish dishes and Type III GBS disease, specifically due to Sequence Type (ST) 283".
Between August and October this year, nearly 400 fish samples across the supply chain - from fishery ports to wholesalers, wet markets, supermarkets and food outlets - were tested by the authorities.
GBS was detected in 20.1 per cent of these samples, while 4.1 per cent of total samples tested positive for the ST283 strain.
The fish that tested positive for the ST283 strain of the bacteria are Song fish (Asian bighead carp), Toman fish (snakehead), and tilapia, which are all freshwater species.
"The contamination of the fish could have occurred along the food supply chain," said the statement issued by the National Environment Agency (NEA), Agri-Food and Veterinary Authority (AVA) and Ministry of Health.
GBS is a bacterium commonly found in the gut and urinary tract of about 15 to 30 per cent of adults without causing any disease. But it may occasionally cause infections of the skin, joints, heart and brain. The risk factors for GBS infection include underlying chronic or co-morbidities, such as diabetes.
With immediate effect, all food stalls selling Chinese-style ready-to-eat raw fish dishes are to stop the sale of all types of raw fish until they can comply with safe practices. These include Song fish and Toman fish.
Food operators who flout this will face action. The raw dish is mostly served by hawkers. When fully cooked, Song and Toman fish are safe for consumption. Japanese sushi and sashimi do not usually use these two types of fish.
In a statement on Friday evening, MOH said it was notified of 355 cases of GBS infections to date this year. Of these, about 150 cases were the GBS strain linked to the consumption of Chinese-style ready-to-eat raw fish dishes.
Among all GBS cases this year, two have died, the statement added. "One death was of a recently reported case and is still under investigation while the other was not linked to the outbreak."
MOH also said since mid-July 2015, following the advisory issued by NEA to licensed food retail establishments to temporarily stop the sale of these raw fish dishes using Song fish and Toman fish, the number of GBS cases notified to MOH has decreased to a usual baseline of less than 5 per week and continues to remain low.
Most of these cases did not report raw fish consumption. The cause of the baseline infections remains unknown.
In August, a 50-year-old technician had both his hands and feet amputated. He had suffered food poisoning after eating a raw fish dish at a food centre in Chinatown. This led to medical complications that required all four limbs to be amputated.
More recently, a 52-year-old man fell into a coma for 10 days after eating a raw fish dish at a hawker centre in Tiong Bahru. He remains in critical condition.
The earlier cases and their possible link to raw fish had made the rounds on social media in July.
In mid-July, the NEA sent out an advisory to stalls to temporarily stop the sale of ready-to-eat raw fish dishes using Song and Toman fish.
The statement said that since the advisory was issued, the number of GBS cases notified to MOH has gone down to the usual baseline of fewer than 5 per week and continues to remain low. The cause of these baseline infections remains unknown.
The statement said food handlers are unlikely to be the source of the bacteria which caused the spike in GBS infections. Stool samples of 82 food handlers and fishmongers were tested and none were found to carry the ST283 strain.
The authorities said that most fish sold at markets and fishery ports here are intended for cooking, and are not safe to eat raw as they may carry parasites or bacteria which are destroyed after cooking.
On the other hand, fish for raw consumption are "typically bred or harvested from cleaner waters, and are stored and distributed according to appropriate cold chain management practices".
This includes transporting the fish at temperatures below 5 degrees Celsius, and packing it separately from other fish meant to be cooked, so as to avoid cross-contamination.