Noroviruses and Norwalk-like Viruses (NLVs) Fact Sheet

What are noroviruses?

Noroviruses are a group of viruses that cause acute gastroenteritis (AGE) in people. The term was recently approved as the official name for this group of viruses. Other names have included Norwalk-like viruses, caliciviruses, and small round structured viruses.

Symptoms and Illness

Norovirus disease is usually not serious, although people may feel very sick and vomit many times a day. Most people get better within 1 or 2 days, with no long-term health effects. Norovirus disease is characterized most frequently by the acute onset of vomiting, watery non-bloody diarrhea and one or more of the following: abdominal cramps, nausea, fever, and headache. Dehydration is the most common complication among the young and the elderly. The incubation period ranges from 12 to 48 hours and the duration of the illness from 12 to 60 hours from onset of symptoms. Infected persons are contagious from the moment they feel ill to at least 3 days after recovery. Some people may be contagious for up to 2 weeks after recovery. It is recommended that ill individuals remain at home for three days after symptoms have resided. Currently, there is no treatment for Norovirus disease. Symptomatic therapy however, replacement of fluids and electrolytes is recommended. If feeling particularly ill, please contact your family physician.

Transmission

Noroviruses are very contagious and can spread easily. Fecal-oral spread is probably the primary transmission mode, although airborne and fomite (contaminated surface) transmission may facilitate the spread during outbreaks. Food and water sources may also be vehicles of transmission. A low infective dose (less than 100 viral particles) allows the virus to spread by droplets, fomites, person-to-person and environmental contacts evidenced by the increased rate of secondary and tertiary spread among contacts and family members.

Prevention

Frequent handwashing with soap and warm water for at least 20 seconds of vigorous rubbing, thorough rinsing with clean water, and drying with disposable towels is recommended. Because of spattering or aerosols of infectious materials may be involved with disease transmission, it is recommended that people who clean areas contaminated by feces and/or vomitus wear masks. Soiled linens should be handled as little as possible and with minimal agitation. Machine washing and drying on the high heat cycle is recommended. Because surfaces have been implicated, soiled surfaces should be disinfected with an appropriate germicide (e.g. 10% solution of bleach in water) according to manufacturers label instructions. Clean and disinfect toilets, toilet levers, sinks, faucet handles, phones, door handles and any other surfaces or equipment that may have become contaminated with feces or vomitus, or that may have been used by an ill person.

For further information contact Northern Nevada Public Health at 328-2434.