Officials in Hong Kong are investigating 40 cases of invasive Group B Streptococcus infection.
The Centre for Health Protection (CHP) of the Department of Health appealed to the public for heightened vigilance and attention when touching or handling raw freshwater fish. Advice included wearing gloves and not consuming undercooked freshwater fish.
CHP and the Hospital Authority have been monitoring the admission figures for invasive Group B Streptococcus infection cases belonging to serotype III sequence type 283 (ST283) since an initial announcement in mid-September.
The 40 patients live in 18 districts. Their illness onset dates are between Aug. 8 and Sept. 5, and 30 have underlying illnesses. In total, 23 cases are female and 17 are male. They range in age between 35 and 94.
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’s epidemiological investigations revealed that 31 patients had contact with 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 issued a letter to doctors to enhance their alertness for Group B Streptococcus infections and said it cannot rule out that the number of cases may increase.
None of the 40 patients were fishmongers or worked in fish-related jobs.
Implicated freshwater fish was bought from 23 markets in 11 districts. CHP and the Agriculture, Fisheries and Conservation Department (AFCD) have inspected the freshwater fish market at the Cheung Sha Wan Wholesale Food Market. Laboratory analysis of environmental samples is still in progress.
The ST283 isolates of environmental and fish samples collected from a retail freshwater fish stall inside the Shek Wu Hui Market are identical to those found in some patients.
CHP and the Food and Environmental Hygiene Department (FEHD) have conducted medical surveillance on 200 workers; no symptomatic person 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 fell sick after eating at a restaurant in Mong Kok. All sick people ate clams in preserved fish sauce.
Cases were six females and three males aged between 28 and 46. Five people sought medical advice, and two required hospitalization. The stool specimen of one affected person was positive for Vibrio parahaemolyticus upon lab testing.
Personnel from the Centre for Food Safety (CFS) of the FEHD inspected the restaurant, took food samples for examination, and instructed the premises to suspend the sale of certain food and carry out cleaning and disinfection. Inadequate cooking and improper hot holding temperature were suspected contributing factors to the incident.
In the second outbreak, 11 tourists fell sick. Cases were eight males and three females aged between 55 and 68. They developed abdominal pain, diarrhea, nausea, vomiting, and fever after having lunch and dinner at two restaurants in To Kwa Wan.
Food items, including cooked shrimp and rice, were the suspected source. Suspected contributing factors were improper hot holding temperature, food prepared too early, and a failure to reheat thoroughly.
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