Officials in Hong Kong are investigating 40 cases of invasive Group B Streptococcus infection.
The Ministry of Health’s Center for Health Protection (CHP) urged the public to exercise increased vigilance and attention when touching or handling raw freshwater fish. The advice included wearing gloves and not consuming undercooked freshwater fish.
CHP and the hospital authority have been monitoring admission rates for cases of invasive Group B Streptococcus infection belonging to serotype III sequence type 283 (ST283) since an initial announcement in mid-September.
The 40 patients live in 18 districts. Their disease onset dates are between August 8 and September 5, and 30 have underlying diseases. A total of 23 cases are female and 17 are male. They range in age from 35 to 94 years.
Ten patients have been discharged, 25 are hospitalized in stable condition, three are in serious condition and two people with underlying illnesses have died.
Link to freshwater fish
CHP epidemiological research found that 31 patients had contacted or handled raw freshwater fish before the onset of symptoms. Five reported having wounds on their hands when handling such fish, and six patients may have consumed undercooked freshwater fish.
CHP has sent a letter to doctors to increase their alertness to Group B Streptococcus infections and said it cannot rule out that the number of cases will increase.
None of the 40 patients were fish sellers or worked in fish-related jobs.
The freshwater fish in question was purchased from 23 markets in 11 districts. CHP and the Ministry of Agriculture, Fisheries and Conservation (AFCD) inspected the freshwater fish market at the Cheung Sha Wan Wholesale Food Market. Laboratory analysis of environmental samples is still ongoing.
The ST283 isolates from environmental and fish samples collected from a freshwater fish stall at Shek Wu Hui Market are identical to those found in some patients.
CHP and the Food and Environmental Hygiene Department (FEHD) provided medical surveillance for 200 employees; no symptomatic individual was identified. FEHD has strengthened the cleaning and disinfection of the relevant markets.
Vibrio outbreaks
Two other recent outbreaks were caused by Vibrio parahaemolyticus.
In the first incident, nine people became ill after eating at a restaurant in Mong Kok. All sick people ate mussels in preserved fish sauce.
It involved six women and three men between the ages of 28 and 46. Five people sought medical advice and two had to be hospitalized. The stool sample from one affected individual was positive for Vibrio parahaemolyticus on laboratory testing.
Personnel from the Center for Food Safety (CFS) of the FEHD inspected the restaurant, took food samples for examination and ordered the premises to suspend the sale of certain foods and to carry out cleaning and disinfection. Inadequate cooking and improper warming temperature were believed to have contributed to the incident.
Eleven tourists became ill in the second outbreak. The cases involved eight men and three women between the ages of 55 and 68. They experienced abdominal pain, diarrhea, nausea, vomiting and fever after lunch and dinner at two restaurants in To Kwa Wan.
Food items, including cooked shrimp and rice, were the suspected source. Suspected contributing factors included improper holding temperature, cooking food too early and not reheating thoroughly.
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