Raw fish dishes were not sold by food stalls visited by patients who recently contracted bacterial infections.

The Group B Streptococcus (GBS) strain that infected about 160 people who ate raw freshwater fish in 2015 was also not detected in routine sampling and testing of fish samples between May last year and this month.

The Singapore Food Agency (SFA), in a joint statement with the Ministry of Health (MOH), yesterday gave an update after a probe.

It had inspected the food stalls visited by the recent patients as part of field investigations on their food history.

The statement followed a circular last Friday from MOH to doctors that said public hospitals reported 50 cases of invasive GBS last month - twice the average monthly figure of 25 from earlier this year.

Laboratory tests showed that 18 of these 50 cases were due to GBS Type III ST283, the same strain that infected about 160 of 360 people in the 2015 outbreak.

A ban on the use of freshwater fish in ready-to-eat raw fish dishes has been in place since December 2015. Saltwater fish can still be used in such dishes.

The ministry said the majority of the cases with GBS Type III ST283 were aged 65 and above, and most of them have since been discharged and recovered from the infection. One died due to an unrelated cause.

The ministry reminded food stalls selling ready-to-eat raw saltwater fish dishes to ensure good hygiene practices and proper handling of the fish.

It also alerted doctors to remain vigilant and report suspected invasive GBS cases.

Vulnerable groups of people should avoid consuming raw food as a precaution, said MOH.

These include young children, pregnant women, elderly persons or people with chronic illness such as diabetes, who may be more susceptible to getting infected.

It also advised people to thoroughly cook their food, wash their hands and utensils before preparing and eating it, and to use separate equipment for preparing cooked and raw food.