SINGAPORE: A Group B Streptococcus (GBS) bacteria strain that caused an outbreak of fish-borne blood poisoning in 2015 is widespread in Southeast Asia, said researchers at Tan Tock Seng Hospital (TTSH) who identified the pathogen.
The strain, called ST283, had landed more than 160 people in hospital with fever and invasive infections, such as meningitis, after they consumed raw freshwater fish.
One of the victims, former technician Tan Whee Boon, lost all his limbs after eating a plate of yusheng, a raw-fish dish. According to past reports, two victims in Singapore died in 2015 from the infection.
DISEASE MORE WIDESPREAD THAN BELIEVED
Researchers said on Wednesday that the disease is more widespread than believed, and has been affecting humans and farmed fish across Southeast Asia for decades.
“ST283 was found in all invasive Asian collections analysed, from 1995 to 2017. It accounted for 76 per cent of human GBS in Laos, 73 per cent in Thailand, 31 per cent in Vietnam, and 23 per cent in Singapore," said TTSH and the Genome Institute of Singapore (GIS) in a press release.
Professor Swaine Chen, group leader of infectious disease at A*STAR’s GIS said that GBS was not thought to be a food-borne disease and no one ever thought to look for it in Southeast Asia.
"The outbreak in 2015 was the first time we had seen GBS-caused food-borne disease. The new data that we have published now demonstrate that this infection has been going on throughout Southeast Asia, not just Singapore, and it has been going on for over 20 years," he said.
The research team published their findings in journal PLoS Neglected Tropical Diseases last month.
In 2015, the Government banned hawker stalls from raw-fish dishes after investigations by MOH found a definite link between eating these dishes and GBS infection, which can potentially cause permanent disability and even death in severe cases.
Dr Timothy Barkham, senior consultant medical microbiologist at the Department of Laboratory Medicine at TTSH said that the ST238 diseases are found mainly in Asia.
"Essentially it’s rare … it's absent elsewhere. There are two to three people in the rest of the world who had it, and ... maybe they caught it by travelling to Asia," he told reporters.
MORE RESEARCH NEEDED
Dr Barkham added that they still do not know why there was such a huge outbreak in Singapore in 2015, but said that the fish may have had more of ST283 in them due to temperature and weather changes.
“It just so happens that in 2014 there was an El Nino year, where temperature records were broken across the region … that doesn’t prove our theory that the degree of contamination is related to temperature (and) the weather, but it supports it," he said.
Dr Barkham also said that it is possible to prevent the spread of bacteria in farmed fish, but this requires collaboration with those in agriculture to provide vaccines for the fish.
“One of the problems we have now is that farmers don't have the money either for the vaccines ... or the resources to know what's wrong with their sick fish,” he said.
“If we could build the infrastructure (to answer) why their fish is dying, this could help tremendously.”
Professor Chen also highlights the importance of more research.
“The new data expands the significance of the outbreak (and) the important problem that we really need to invest more resources in researching,” he said.
DON'T EAT RAW RIVER FISH HERE OR OVERSEAS
Researchers said that Singaporeans should continue to observe the advisory issued by MOH and AVA in 2015, and cook their freshwater fish before consuming them.
Singaporeans should also avoid consuming raw or under-cooked fish when travelling to neighbouring countries.
“These measures will prevent them from being infested or being at risk of carrying the strain back home.
“Cooking raw food thoroughly with sufficient heat is still the most effective way to destroy microbial pathogens - ensuring the fishes are safe to eat."
In a response to CNA's queries, the Singapore Food Agency (SFA) said that food establishments in Singapore can only serve raw saltwater fish, which are "closely monitored and tested for safety".
"Members of the public should note that there are always risks involved in consuming raw fish as harmful bacteria and parasites may be present," it said.
"Should one choose to consume raw fish, the risk of food borne illness can be reduced by purchasing fish that are intended for raw consumption."
It also advised that young children, pregnant women, the elderly, or people with chronic illnesses, in particular, should avoid eating raw fish.
This story has been updated with the Singapore Food Agency's response.