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Winter 2003 - Article 5

Disinfectant Update
The Norwalk Virus

Recent cruise ship intestinal illness outbreaks have focused a lot of attention on Norwalk and Norwalk-like viruses, now being referred to as Norovirus by the scientific community. These viruses are increasingly being recognized as the leading cause of foodborne disease in the United States. In addition to cruise ships, the virus is commonly found where a large amount of people are concentrated in a small area such as daycare centers, summer camps, schools and households.

People contract Norwalk virus (NV) by swallowing food or water that has been contaminated with the 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 that can carry the viruses.

Norwalk virus was first identified in 1972 after an outbreak of gastrointestinal illness in an elementary school in Norwalk, Ohio, in 1968. Later, other viruses with similar features were described and called Norwalk-like viruses. These have since been classified as members of the Calicivirus family.

The signs and symptoms of Norwalk virus include nausea, vomiting, diarrhea and stomach cramps. Severe illness or hospitalization is uncommon. Infected persons usually recover in two or three days without any health side effects. No specific treatment is available. Persons who are severely dehydrated may need rehydration therapy.

There are currently no EPA-approved protocols for testing against Norwalk virus, so no disinfectants carry the Norwalk “kill claim”. The virus cannot be grown on a medium through conventional means, making it impossible to test for efficacy. Because of news reports and heightened awareness, the EPA is considering approving a surrogate test media called Feline Calicivirus. This is the same approach the EPA took with HBV, approving a duck egg surrogate test.

Update (1-2-07): Quat 44 (#2318DN) and Restroom Cleaner and Disinfectant #7 (#2319SC) are now labeled for use against Norwalk virus.

Bleach is often recommended to control NV, but it is ineffective since the protein shell called the Norovirus capsid, is resistant to chlorine. High concentrations of bleach (>800 ppm) are sometimes recommended, but this is not safe. Bleach at this concentration should not be inhaled and is very corrosive.

Is there any prevention for NV? There are only a couple of things that can be done. They include:

• Washing hands with soap and warm water after restroom visits, before preparing or eating food and after caring for the sick.
• Limiting person to person contact if you are NV symptomatic.
• Excluding persons with gastroenteritis from handling food.