Food Safety Focus (224th Issue, March 2025) – Article 1
Review of Food Poisoning Outbreaks Related to Food Premises and Food Business in 2024
Reported by Dr. Choi Yuk Kiu, Senior Medical & Health Officer,
Risk Management Section, Centre for Food Safety
This article reviews the food poisoning outbreaks (FPO) related to local food premises and food businesses reported to the Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department (FEHD) in 2024.
Food poisoning outbreaks is a statutory notifiable disease in Hong Kong under the Cap 599 Prevention and Control of Disease Ordinance. All medical practitioners are required to notify the Department of Health (DH) of all suspected FPOs. The number of reported FPO related to food premises fluctuated in the past decade, ranging from 117 to 256 cases per year. In 2024, the CFS received 192 food poisoning cases referred by the DH, affecting 739 individuals (see Figure). FEHD will inspect all the concerned food premises for investigation.
Figure: Number of food poisoning outbreaks related to food premises and food business and the corresponding number of persons affected from 2015 to 2024
Causative Agents and Contributing Factors
As some of the FPO reported by the CHP in 2024 involved more than one pathogens, resulting in the total percentage of causative agents exceeding 100%. In 2024, the top 3 causative agents for all FPO were Norovirus (46.9%), Salmonella (34.4%) and Vibrio parahaemolyticus (28.1%). Biochemical cases (e.g., ciguatoxin, shellfish toxin) and chemical case account for 4.2% and 0.5% of all FPO. Overall, "consumption of raw food", "contamination by utensil" and "inadequate cooking" were the three most common contributing factors in all FPO.
| Causative agent | Percentage # |
| Norovirus | 46.90% |
| Salmonella spp. | 34.40% |
| Vibrio parahaemolyticus | 28.10% |
| Biochemical cases (e.g. Ciguatoxin, shellfish toxin) | 4.20% |
| Chemical case | 0.50% |
| # As epidemiological investigation could not clearly define the causative agent (e.g. due to lack of clinical samples), therefore more then one type of causative agents (e.g. Norovirus and Salmonella) could be referred in one case. | |
Highlights of FPO in 2024:
(i) Food poisoning clusters related to Vibrio parahaemolyticus and undercooked clams
There were a total of four linked cases affecting 15 persons referred to the CFS for this FPO. The CFS immediately conducted a site visit to the food premises upon notification. Investigation by the CFS revealed irregularities in food handling of clams in the concerned food premises. The clams were just briefly cooked and being placed at room temperature for few hours for cooling. Upon order, food handlers would mix the home-made sauce (prepared with chilli, garlic, and wine) with the clams and served it to customers without further cooking or reheating. The CFS collected a food sample of clams for testing and it was tested positive for Vibrio parahaemolyticus.
Control measures were implemented immediately including suspending the sale of the clam dish, conducting thorough cleaning and disinfection of the food premises, reviewing and improving the food production process. Health education was provided to the food handlers and their management, emphasizing the importance of adequate cooking, reheating and careful estimation of dish demand to avoid over-production. No more linked FPO was received by the CFS after the introduction of control measures in the food premises.
(ii) Food Poisoning Outbreaks involving Norovirus in 2024
There were an increasing number of Norovirus food poisoning outbreaks cases referred to the CFS in 2024. Norovirus is most commonly related to the consumption of raw or undercooked shellfish. In 2023, Norovirus was implicated as the suspected cause in 25.7% of all FPO, and the consumption of raw oysters was the predominant cause. In 2024, Norovirus FPO notification increased to 46.9% of all FPO, and a wide array of food items were involved. Consumption of ready to eat raw oysters contributed to two-thirds of the Norovirus outbreak. Others were related to consumption of undercooked seafood (other than raw oysters) and consumption of contaminated ready to eat food (such as siu mei, salad and dessert).
In addition to the inherent risk associated with raw shellfish, the diversity in other food items suggests the role of cross contamination in Norovirus food poisoning outbreaks. Norovirus is a highly contagious and can easily spread via person to person, contaminated object/ environment, food, water and cause gastroenteritis. Proper cleaning and disinfection and proper food handling should be emphasised in the control of Norovirus outbreaks in these food premises. The CFS has instructed the concerned food premises to use 1:49 diluted household bleach containing 5.25% sodium hypochlorite for thorough cleaning and disinfection, and leave for 15-30 minutes to allow time for the bleach to inactivate the viruses; then rinse with water and wipe the area dry. Moreover, the CFS provided health education material on norovirus and health talks for food handlers, emphasising the importance of handwashing with soap and water after using the toilet, before handling food, and before eating. Notably, alcohol-based hand sanitizers are ineffective against Norovirus and should not replace proper hand washing procedure. Sick food handlers should report to their management and suspend from engaging in any work related to contact with food, food contact surfaces and food utensils until recovery.
Conclusion
Overall, the number of food poisoning outbreaks fluctuated in the past decade. Salmonella, Vibrio parahaemolyticus and Norovirus remain to be the main causes of FPO. It is important for the management of the food business to implement "Five Keys to Food Safety" and start to introduce more food safety training to staff and implement the monitoring system (such as safe cooking and keeping temperature and prevention of contamination to cook food) in the food premises.
