Be Prepared for Norovirus This Winter

There are a number of reported outbreaks of norovirus in North America, and it behooves infection preventionists in acute care and long-term care to be prepared for an influx of cases at their institutions.

Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. The most common symptoms of acute gastroenteritis are diarrhea, vomiting, and stomach pain. Norovirus is the official genus name for the group of viruses previously described as "Norwalk-like viruses" (NLV).

Noroviruses spread from person to person, through contaminated food or water, and by touching contaminated surfaces. Noroviruses are found in the stool and vomit of infected people. People can become infected by:

- Eating food or drinking liquids that are contaminated with norovirus.

- Touching surfaces or objects that are contaminated with norovirus, and then placing their hand in their mouth.

- Having direct contact with an infected person; for example, by exposure to the virus when caring for or when sharing food, drinks, or eating utensils with an infected person.

Norovirus is recognized as the leading cause of foodborne-disease outbreaks in the United States. Outbreaks can happen to people of all ages and in a variety of settings.

Noroviruses are responsible for about half of all reported outbreaks of gastroenteritis (vomiting, diarrhea, and stomach cramping caused by inflammation of the stomach and intestines). While the vast majority of norovirus illnesses are not part of a recognized cluster, outbreaks provide important information on how the virus is spread and, therefore, how best to prevent infection. Norovirus outbreaks occur throughout the year, but more than 80 percent of them occur from November to April. In addition, norovirus outbreaks tend to increase periodically when new strains of the virus appear. The virus can be spread through food, water, by touching things that have the virus on them, as well as directly from person to person. There is no long-lasting immunity to norovirus; thus, outbreaks can affect people of all ages and in a variety of settings.

Healthcare facilities, including nursing homes and hospitals, are the most commonly reported settings for norovirus outbreaks in the United States and other industrialized countries. The virus can be introduced into healthcare facilities by infected patients--who may or may not be showing symptoms--or by staff, visitors, or contaminated food products. Outbreaks in these settings can be quite longsometimes lasting monthsand illness can be more severe, occasionally even fatal, in hospitalized or nursing home patients than for otherwise healthy persons.

While most norovirus outbreaks are investigated by state and local public health authorities, the Centers for Disease Control and Prevention (CDC) provides coordination of norovirus outbreaks that involve multiple states. Such multi-state outbreaks may result, for example, from a contaminated food that has been widely distributed to various states or from an event that involves participants from multiple states. When requested, CDC also provides technical consultation and assistance to state and local public health agencies during norovirus outbreaks. CDC is also working to improve state and local laboratory capacity and can provide diagnostic support, if requested, to help confirm and report norovirus outbreaks.

Tips from the CDC to prevent the spread of norovirus:

- Practice proper hand hygiene: Wash your hands carefully with soap and water, especially after using the toilet and changing diapers and always before eating or preparing food. Alcohol-based hand sanitizers (containing at least 62 percent ethanol) may be a helpful addition to handwashing, but they are not a substitute for washing with soap and water.

- Take care in the kitchen: Carefully wash fruits and vegetables, and cook oysters and other shellfish thoroughly before eating them.

- Do not prepare food while infected; people who are infected with norovirus should not prepare food for others while they have symptoms and for three days after they recover from their illness.

- Clean and disinfect contaminated surfaces. After an episode of illness, such as vomiting or diarrhea, immediately clean and disinfect contaminated surfaces by using a bleach-based household cleaner as directed on the product label or a solution made by adding five to 25 tablespoons of household bleach to 1 gallon of water.

- Wash laundry thoroughly: Immediately remove and wash clothing or linens that may be contaminated with vomit or fecal matter. Handle soiled items carefullywithout agitating themto avoid spreading virus. They should be laundered with detergent at the maximum available cycle length and then machine dried.