Office of Communicable Diseases

Norovirus Infection

Noroviruses are increasingly being recognized as the leading causes of foodborne disease in the United States, and have been linked to outbreaks of intestinal illness on cruise ships and in communities, restaurants, camps, schools, institutions, and families. This fact sheet provides information about the virus and includes preventive measures to reduce or eliminate further illness.

What is norovirus infection?
Norovirus infection is an intestinal illness that often occurs in outbreaks. The virus was first identified in 1972 after an outbreak of gastrointestinal illness in Norwalk, Ohio. Later, other viruses with similar features were described and called Norwalk-like viruses. These have since been classified as members of the calicivirus family.

Where is norovirus found?
Noroviruses are found worldwide. Humans are the only known hosts. The viruses are passed in the stool of infected persons.

How do people get norovirus infection?
People get norovirus infection by swallowing food or water that has been contaminated with stool from an infected person. Outbreaks in the United States are often linked to eating raw shellfish, especially oysters and clams. Shellfish become contaminated via stool from sick food handlers or from raw sewage dumped overboard by recreational and/or commercial boaters. Contaminated water, ice, eggs, salad ingredients, and ready-to-eat foods are other sources of infection.

Why is norovirus infection important for food handlers?
Food handlers infected with norovirus can unintentionally contaminate the food and/or beverage they prepare and serve to the public. Many of those eating the contaminated food or drinking the contaminated beverage can become ill, causing an outbreak. Even if the food handler no longer feels ill, they can still carry the virus in their stool and potentially infect others. Therefore, the RI Department of Health requires that food handlers not work for 2 days after they feel better.

Who is at risk for norovirus infection?
Anyone can get norovirus infection, but it may be more common in adults and older children.

What are the signs and symptoms of norovirus infection?

• Nausea
• Vomiting
• Diarrhea
• Stomach cramps
• Severe illness or hospitalization is uncommon. Infected persons usually recover in 2 to 3 days without serious or long-term health effects.

How soon after exposure do symptoms appear?
Symptoms usually appear in 1 to 2 days after swallowing contaminated food or water.

How is norovirus diagnosed and what is the treatment for Norovirus infection?
Currently, 27 state public health laboratories, including RI, have the capability to test stool samples of infected individuals for norovirus by reverse transcriptase polymerase chain reaction (RT-PCR). No specific treatment is available. Persons who are severely dehydrated might need rehydration therapy.

How can norovirus be prevented?

• Wash hands with soap and warm water after toilet visits, changing a diaper, blowing your nose, sneezing or coughing, caring for a sick person, playing with a pet, and also before preparing or eating food (For additional information, refer to “Things to Do to Prevent Infectious Diseases”)
• Dispose of sewage in a sanitary manner
• Thoroughly clean and disinfect contaminated surfaces immediately after an episode of illness by using a bleach-based household cleaner. Wash and wipe down the toilet area, faucets and similar hard surfaces with a mixture of one tablespoon of bleach to 3 cups of water. If cleaning up vomit or stool, use two tablespoons of bleach to 1 cup water.
• Cook all shellfish thoroughly before eating
• Wash raw vegetables and fruits before eating
• No bare-hand contact of ready-to-eat food by food handlers
• Food handlers with symptoms of Norovirus illness should not prepare or touch food

Where can I get more information on noroviruses?
The Centers for Disease Control has additional information.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have any questions about the disease described above, consult a health-care provider. (Adapted from the Association of State and Territorial Directors of Health Promotion and Public Health Education and the Centers for Disease Control and Prevention)