Food poisoning

Overview

Gastroenteritis refers to the inflammation of the stomach and intestines, often caused by infections from bacteria, parasites, or viruses. Some bacteria cause the symptoms of gastroenteritis by releasing toxins. When the infection is caused by a virus, it is known as viral gastroenteritis, commonly referred to as the "stomach flu".

Pathogen(s)

Some foodborne pathogens causing food poisoning include:

• Norovirus

• Salmonella spp. (non-typhoidal)

• Staphylococcus aureus

• Clostridium perfringens

• Bacillus cereus

• Escherichia coli

Transmission

Mode of transmission: Contaminated food or water or person-person spread/contact with contaminated surfaces.

Incubation period: Depending on the pathogen and ingested dose, it can vary from hours to days.

Infectious period: Depends on the pathogen.

Clinical features

Majority of food-borne illness present with acute gastrointestinal symptoms:

• Nausea

• Vomiting

• Diarrhoea

• Abdominal pain

• Fever may or may not be present. It is typically absent when caused by toxin-producing organisms.

Risk factors

Consumption of contaminated food or water or contact with infected persons or fomites.

Diagnosis

Appropriate specimens for laboratory confirmation vary depending on the clinical presentation but typically include patient’s stools or blood.

Treatment and management

Rehydration (either oral or intravenous) remains the mainstay therapy.

Patients with bloody diarrhoea, high fever, dehydration, and failure to retain fluids should be considered for admission.

Antimicrobial agents are of no value in the management of viral gastroenteritis.

Precaution, prevention, and control

Standard and contact precautions (if active diarrhoea) apply in healthcare settings.

To reduce the risk of having gastroenteritis:

• Avoid contaminated food: Wash all fruits and vegetables thoroughly before eating and cook meat completely (avoid undercooked meat or fish). Avoid unpasteurised milk or untreated water, especially when travelling overseas. Ensure food (especially filter feeders e.g. oysters and shellfish) is thoroughly cooked before eating.

• Adopt proper hand hygiene: Wash hands with soap and water regularly, especially after using the toilet, before having meals, after gardening or playing with pets.

• Environmental cleaning: Disinfect surfaces contaminated with diarrhoea or vomitus immediately by using 1 part household bleach (5.25%-6.15% sodium hypochlorite) to 9 parts water. Leave the bleach disinfectant on the affected area for at least 10 minutes. Wash contaminated clothing or linens immediately.

• Immunisation: Vaccinate with the rotavirus vaccine to protect young children from rotavirus, which is one of the most common causes of gastroenteritis in children. 

Patients should be advised not to prepare food for others while sick and for at least 2 days after symptoms resolve.

Food handlers whose stool samples test positive for foodborne pathogens would be temporarily suspended from food handling duties by the Communicable Diseases Agency. 2 subsequent negative stool test results, with samples taken at least 1 week apart and collected securely from the individual, are required before their suspension will be lifted.

Notification

Clusters of food poisoning should be notified to the Communicable Diseases Agency to facilitate investigations.

Who should notify:

• Medical practitioners

When to notify:

• On clinical suspicion

How to notify:

• Please refer to the Infectious Disease Notification for more information.

Notification timeline:

• As soon as possible

Resources

Please refer to the Weekly Infectious Diseases Bulletin for the number of confirmed foodborne poisoning/ illness cases in Singapore.