Three days after Mr Tan Hwee Boon, 50, ate a raw fish dish, or yusheng, he showed symptoms of food poisoning.
A diagnosis at Khoo Teck Puat Hospital (KTPH), however, revealed that the technician had severe pneumonia that was complicated by sepsis that led to gangrene on his hands and feet.
Mr Tan was eating the dish with his primary school maths teacher, who had also ordered the same dish at a food centre in Chinatown.
His former teacher was unaffected by the meal.
The doctors are still looking into the exact cause of his condition but initial investigations found three types of bacteria in Mr Tan's body.
KTPH's medical team said Mr Tan's condition could have been caused by any strain of the bacteria, or a combination.
One of them is Group B Streptococcus (GBS), a bacterium commonly found in the gut and urinary tract of about 15 to 30 per cent of adults without causing any disease.
GBS, however, 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.
RAW FISH RISK
GBS can also be found in fish, but this does not pose an issue if the fish is well cooked before consumption.
Last month, the Ministry of Health launched an investigation into a limited number of identified cases and found an association between raw fish consumption and GBS infections.
More cases will need to be studied for a more definitive conclusion, the ministry said.
KTPH's medical team said it is still looking into any possible link between Mr Tan's condition and the raw fish he had eaten.
This article was first published on Aug 14, 2015.
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