Food Safety Focus Banner

To the main pageNext Article

Food Safety Focus (179th Issue, June 2021) – Incident in Focus

Review of Food Poisoning Outbreaks Related to
Food Premises and Food Business in 2020

Reported by Dr. Lousia CHOI, Medical & Health Officer,
Risk Management Section, Centre for Food Safety

This article reviews the FPOs related to local food premises and food business reported to the Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department in 2020.

Food Poisoning Outbreaks Related to Local Food Premises and Food Business

In 2020, the CFS received 229 referrals of FPOs, affecting 632 persons in total. Since the global COVID-19 pandemic, takeaway foods have become more popular among the general public. The number of food poisoning outbreaks (FPOs) related to takeaway foods increased from 36 cases (19.5% of total FPOs) affecting 236 persons in 2019 to 128 cases (55.9%) affecting 331 persons in 2020. While a generally decreasing trend in the number of FPOs since 2012 was noted (see Figure 1), there was a small rebound in 2019 and 2020. Last year’s increase was mainly attributable to one large-scale cluster involving 99 epi-linked outbreaks related to sandwiches. Despite more FPOs were recorded compared with 2019, the number of affected persons hit record low in 2020.

Number of food poisoning outbreaks related to food premises and food business and the corresponding number of persons affected from 2010 to 2020.

Figure 1: Number of food poisoning outbreaks related to food premises and food business and the corresponding number of persons affected from 2010 to 2020.

Causative Agents and Contributing Factors

Bacterial foodborne agents remained the leading causes (90%) of all FPOs in 2020, and Salmonella (76.3% of all bacterial cases) topped the list, followed by Vibrio parahaemolyticus (16.9%) and Bacillus cereus (2.9%). Viral causes accounted for 7% of all the FPOs, with Norovirus virtually involved in all viral cases. Natural toxin cases (such as mushroom toxins, ciguatera toxins, etc., 2.6%) and chemical case (calcium oxalate, 0.4%) contributed to the remaining FPOs. Contamination by raw food, contamination by food handlers and improper holding temperature were the three most frequently identified contributing factors.

Highlights on Major Epi-linked Food Poisoning Outbreaks in 2020

Food Poisoning Outbreaks involving Sandwiches related to Salmonella species

In May 2020, the CFS received 99 epi-linked FPOs related to the consumption of prepackaged sandwiches of the same brand, involving 236 persons. Stool samples of 42 affected persons yielded Salmonella. One victim required intensive care and the blood specimen grew Salmonella Enteritidis. Group D Salmonella was also detected in one of the unconsumed sandwiches bought by a victim.

The sandwiches were produced by a local food factory. Field investigation revealed a number of  contributing factors to the outbreaks, including ready-to-eat ingredients being contaminated by raw ingredients and food handlers, improper holding temperature during transportation of the sandwiches to the retail outlets, and improper storage temperature of finished products at the temperature danger zone allowing pathogens to grow. In addition, the manufacturer did not provide the production date and expiry date on the packing of the sandwiches for staff and customers' information. A sandwich sample collected from an outlet was tested positive for Group D Salmonella.

The CFS instructed the food factory and retail outlets to stop the sale of all sandwiches immediately and carry out thorough cleansing and disinfection. Health advice was conveyed to the food handlers.  The CFS issued press releases to urge the public not to consume the concerned sandwiches. The food factory operator has ceased operating the concerned food business since then.

Sandwich preparation often involves manual handling and prepacked sandwiches produced by food factories can be distributed widely. Thus, stringent food safety and hygiene practices should be adopted in food factories to avoid contamination. As illustrated in this case malpractice in any step could lead to large-scale FPOs affecting a large number of people.

Food Poisoning Outbreaks involving Takeaway Lobster Noodles related to Vibrio parahaemolyticus species

In September 2020, seven epi-linked FPOs involving 19 persons were reported, involving takeaway lobster noodles purchased from a restaurant.  A victim's stool sample grew Vibrio parahaemolyticus (VP). Investigation revealed that the cooked lobsters were prepared too far in advance to cater for the high demand during busy hours, and might have been contaminated by food handlers and other raw seafood. Health advice regarding personal hygiene, food and environmental safety was provided to the concerned food premises and the sale of the food item was suspended immediately. The premises was thoroughly cleaned and disinfected, and no further related FPOs were received afterwards.

To prevent VP infection, it is important to cook food thoroughly, observe good hygiene practices, and prevent cross-contamination after cooking by raw seafood.


The large-scale sandwich related FPO in 2020 served as a reminder to food trade that failure to adopt stringent food safety practices and lapses in personal and environmental hygiene can cause serious health hazards to the public. Takeaway foods have become more popular since the COVID-19 pandemic. The trade and the public should stay alert to the risks involved and adhere to the 'Five Keys to Food Safety' to prevent occurrence of FPOs.