Noroviruses are a group of viruses that are responsible for causing an estimated 21,000,000 cases of intestinal illness in the United States every year. Norovirus used to be called Norwalk virus but was renamed when it was determined that there was more than one type of virus in this group. It is very contagious and can infect anyone. Norovirus is often connected to outbreaks on cruise ships and in childcare facilities. Ill people are most contagious throughout their illness and for the first three days after they have recovered. Norovirus can stay on surfaces and still be able to make others sick days or weeks later. Since there are several different types of norovirus, people can be infected many times in a lifetime.

The period from ingestion to feeling ill is called the “incubation period”. The incubation period for this illness is usually within one to two days after exposure but may be as little as twelve hours. The common symptoms include vomiting (explosive and projectile), watery diarrhea that is not bloody and cramps. Most people recover within a day or two. Those at high risk such as the very young, elderly and patients sick with other illnesses can have more severe problems.

There are no medicines such as antibiotics available for treatment of this illness. No vaccination can be given to prevent norovirus illnesses. People with the most severe symptoms should see a health care professional to determine if hospitalization is required. Most people just need plenty of fluids to prevent dehydration when they have this illness.

Contaminated water or food are the source of outbreaks of norovirus with transmission occurring through person to person contact and contact with contaminated surfaces. Tips for preventing the spread of this illness can be found on our tips page. To reduce the potential spread of Norovirus additional control measures may be required for persons associated with high-risk activities or settings such as food handlers, childcare facility personnel, and health care workers. Specific guidance and recommendations can be found in a manual titled Prevention and Control of Communicable Diseases. Additional guidance for retail food establishment management can be found in Chapter 2 of the food code.

For additional information on Norovirus, please visit the following references: Centers for Disease and Control and Prevention website and FDA’s Bad Bug Book. For data on reported Norovirus cases in Missouri, visit the communicable disease data and statistical reports page for the annual reports listed there.