Overall incidents down slightly but oyster outbreaks increase in Hong Kong

Overall incidents down slightly but oyster outbreaks increase in Hong Kong

The number of foodborne outbreaks in Hong Kong declined this past year, according to recently released figures.

Statistics cover outbreaks related to food premises and businesses that were reported to the Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department in 2021.

The CFS received 199 referrals of outbreaks that affected 608 people compared to 229 outbreaks with 632 patients in 2020.

Vibrio climbs above Salmonella
Bacterial foodborne agents remained the leading cause and were behind two thirds of outbreaks in 2021. Vibrio parahaemolyticus overtook Salmonella as the top agent responsible for illnesses. Other causes were Staphylococcus aureus, Bacillus cereus and Clostridium perfringens.

Viruses accounted for more than a quarter of food poisoning outbreaks, all being norovirus. A few incidents were linked to poisonous mushrooms and ciguatera.

Contamination by raw food, consumption of raw food and inadequate cooking were the most frequently identified contributing factors.

The number of outbreaks and people sick has been steady in Hong Kong for the past three years.

“In 2021, lapses in food safety practices in relation to raw oysters led to a number of outbreaks which added significantly to the toll. This illustrates that lapses in hygiene practices by a small sector of the trade can affect a large number of consumers.”

Raw oyster focus
The CFS noticed an increase in outbreaks traced to raw oysters in 2021 with 101 epidemics and 326 patients. The five-year average was 24 outbreaks per year in 2016 to 2020. Storage temperature and wet storage were the main issues identified.

The largest cluster included 32 linked outbreaks involving a restaurant and affecting 99 people in October 2021. The infections were caused by Vibrio parahaemolyticus.

An investigation revealed refrigerators for ready-to-eat seafood at the restaurant were defective. According to staff, the refrigerators had been malfunctioning for two to three days before the date of consumption mentioned by affected people. The temperature was higher than 4 degrees C (39.2 degrees F). Refrigerators were also overfilled with food, which may have affected cooling ability.

Wet storage of raw oysters, including mixing and putting oysters of different origins in the same tank, was identified in a number of outbreaks. Wet storage is the storing live shellfish temporarily by submerging the under water or spraying them with water and the practice is not advised by authorities in other countries after oysters have been packed.

The CFS said that raw oysters should only be eaten in or obtained from licensed premises. The public should not eat oysters raw that are intended for consumption after cooking. The agency also reminded industry of the importance of hygiene and not to practice wet storage of raw oysters.

In December, the Centre for Food Safety and environmental hygiene branch of the Food and Environmental Hygiene Department (FEHD) enhanced inspections at licensed food premises across the territory to ensure oysters to be eaten raw were stored at the correct temperature.

Warning letters were issued at two food factories suspected of breaching licensing conditions by keeping raw oysters at an improper temperature. The rules state all oysters ready for consumption must be kept in a refrigerator or compartment of a fridge separated from other food items at a temperature between zero and 4 degrees C (32 to 39.2 degrees F).

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