Public Health - Dayton & Montgomery County

General Information on Norovirus

Norovirus generally peaks February to April every year.  Noroviruses (previously known as Norwalk-like viruses) are widely known for causing acute gastroenteritis in humans.  While their presence in cruise ship outbreaks is highly publicized, they also are responsible for up to 60% of foodborne illnesses in the United States according to the Centers for Disease Control and Prevention.  Noroviruses are also becoming more frequently associated with outbreaks in healthcare facilities and schools.

The onset time for Norovirus-associated gastroenteritis is 12 to 48 hours, with a median of approximately 33 hours.  Illness includes sudden onset of vomiting, watery, non-bloody diarrhea with abdominal cramps, and nausea.  Headache and muscle ache are also common.  Low-grade fever is present in about half of cases.  Duration of symptoms is 24 to 48 hours with dehydration the most common complication.

Noroviruses are highly contagious, with as little as 100 virus particles thought to be sufficient to cause infection.  Noroviruses are transmitted primarily through the fecal-oral route, either by direct person-to-person spread or fecally contaminated food or water.  These viruses can also be spread via the droplet route from vomitus.  Norovirus particles are present in the feces and vomit of infected individuals at very high levels (millions per gram).  In health care and institutional settings, persons may become ill by touching contaminated surfaces and then touching their mouths, or having direct contact with an infected person.  Studies have shown that some noroviruses may persist on hard surfaces for as long as 21 days.

Due to the capability of noroviruses being transmitted via environmental surfaces or inanimate objects, disinfection of facilities may be required during outbreak situations to stop the spread of the illness.  A person’s best defense against norovirus is strict handwashing.

Disinfection for Norovirus in Healthcare Facilities and Schools

Examples of items to disinfect: 
Doorknobs, faucets, sinks, toilets, stall dividers and doors, bath rails, phones, counters, chairs, tables, hand rails, elevator buttons, light switches and floors.

What to use:
Chlorine bleach (sodium hypochlorite)
1000 ppm (parts per million)
1/3 cup bleach in 1 gallon of water (1:50 dilution)

Mix bleach with warm water, (water that is too hot will dissipate the chlorine), apply to surfaces and allow to air dry.  Staff should use appropriate PPE (personal protective equipment) when working with bleach, ie: goggles and gloves.

Note: Many institutions use some form of quaternary ammonium compound in their facilities.  Many quaternary ammonium compounds are also effective against noroviruses. 

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