Foodborne Illness – Norwalk-Like Virus

Common names for illnesses from Norwalk and Norwalk-like viruses are viral gastroenteritis, acute nonbacterial gastroenteritis, food poisoning, and food infection.

Symptoms

The disease is usually mild and brief. It will develop 24 to 48 hours after consumption of contaminated food or water and lasts for 24 to 60 hours. Symptoms include:

• Nausea
• Vomiting
• Diarrhea
• Abdominal pain
• Headache and low-grade fever may occur

How It Is Spread

• Norwalk gastroenteritis is transmitted by the fecal-oral route via contaminated water and foods. The infectious dose is unknown but presumed to be low.
• An infected person may spread the illness to others by failing to wash hands thoroughly after a bowel movement.
• Secondary person-to-person transmission has been documented.
• Water is the most common source of outbreaks and may include water from municipal supplies, wells, recreational lakes, swimming pools, and water stored aboard cruise ships.
• Shellfish and salad ingredients are the foods most often implicated in Norwalk outbreaks. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with Norwalk virus.
• Foods other than shellfish are contaminated by ill food handlers.

Diagnosis & Treatment

• Identification of the virus can be made from stool samples collected early in the course of the illness.

Prevention

• Wash hands well after going to the bathroom, after changing diapers, after animal contact, and before and after preparing food.
• Protect water supplies from human and animal waste.
• Drink and use only pasteurized milk.
• Cook food thoroughly.