Authorities in Singapore are investigating an increase in Group B Streptococcus (GBS) cases.

GBS infections had previously been associated with eating raw freshwater fish and the Ministry of Health (MOH) and Singapore Food Agency (SFA) advised those who consume ready-to-eat (RTE) raw fish to exercise caution.

In July 2020, the MOH received reports of 50 GBS patients from public hospitals compared with an average of 25 GBS cases per month from January to June.

Spike in reports
Laboratory investigations showed that 18 cases in July were GBS serotype III sequence type (ST) 283. This compares with an average of four per month from April to June. Most people with GBS Type III ST283 were aged 65 and above. The majority have since been discharged and recovered from their infections while one person died because of an unrelated cause.

MOH and SFA are collecting information on the affected individuals’ food history and conducting field investigations, to determine possible sources of GBS in these patients.

Based on SFA’s routine sampling and testing of fish samples for GBS between May 2019 and August 2020, the presence of ST283 has not been detected. SFA also inspected food stalls visited by recent cases and found that none of them sold any RTE raw fish dishes.

Ban and previous outbreak
SFA is reminding retail food establishments there is a ban on use of freshwater fish for sale of RTE raw fish dishes, which has been in force since December 2015. Food sites selling RTE raw fish should also ensure good hygiene practices and proper handling of fish.

A major outbreak of GBS infection associated with eating a Chinese-style raw fish dish called yusheng occurred in Singapore during 2015 and involved 238 people during the first half of the year compared with an average of 150 cases per year in the four years before 2015.

GBS is a common bacterium found in the human gut and urinary tract of about 15 to 30 percent of adults without causing disease. However, it may cause invasive infections of the skin, joints, heart and brain. Risk factors for infection include underlying chronic or co-morbid conditions, such as diabetes. Transmission may also occur during childbirth. Most GBS infections are treatable with antibiotics.

As a general precaution, vulnerable groups, especially young children, pregnant women, elderly persons, or people with chronic illness, may be more susceptible and should avoid consumption of raw food. Individuals can also reduce the risk of infection by thoroughly cooking food; washing hands and kitchen utensils such as knives and cutting boards thoroughly before handling food; and using separate sets of knives and cutting boards for raw and cooked food.

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