Norovirus: The “Stomach Flu” That is Not a Flu

Norovirus is a highly contagious virus that causes flu-like symptoms of nausea, vomiting, diarrhea and abdominal cramping.Norovirus is a highly contagious virus that causes flu-like symptoms of nausea, vomiting, diarrhea and abdominal cramping.

(Image from CDC website)

The dreaded “stomach flu” that hits particularly hard in winter is not a flu at all. It is norovirus, a highly contagious virus that causes symptoms of diarrhea, vomiting and stomach cramping. According to the Centers for Disease Control and Prevention (CDC), the illness often begins suddenly and lasts for one to two days with no long-term adverse health effects. True “flu” is a respiratory disease caused by the influenza viruses; sometimes the “true flu” can also cause gastrointestinal symptoms similar to norovirus. Getting an annual flu vaccine can help prevent flu; unfortunately, there is no vaccine for the norovirus and antibiotics, useful only for bacterial infections, do not help.

Norovirus is extremely common and has gained notoriety as a vacation cruise spoiler and an unwelcome visitor in child and adult care facilities, schools, restaurants, hospitals and dormitories. Norovirus particles are extremely small and are discharged by the billions in the stool or vomit of infected people, according to CDC. Yet, fewer than 100 virus particles are highly likely to make a person sick. The virus spreads through direct contact with an infected person or when an individual touches a contaminated surface and then touches their mouth or even their nose.

A 2011 study found norovirus is the leading cause of foodborne illness in the US, responsible for 5.5 million cases each year. In many cases, sick food handlers are responsible for these outbreaks. Eating foods contaminated with norovirus is a leading cause of hospitalizations.

Recipe for an Outbreak

Close quarters and a breakdown in sanitation is the simple recipe for a norovirus outbreak. Attention to surface disinfection is critical to controlling the spread of norovirus. Proper hand washing is another “must” as the virus can be transmitted easily via contaminated hands. It is important to know that a norovirus carrier can infect others for at least three days after recovery.

These steps, from CDC, can help reduce your risk of contracting norovirus:

  • Wash your hands carefully with soap and water, especially after using the toilet and changing diapers and always before eating or preparing food.
  • Carefully wash fruits and vegetables, and cook oysters and other shellfish thoroughly before eating them.
  • If infected with norovirus, do not prepare food for others while experiencing symptoms and for three days after recovery (see Norovirus: Food Handlers).
  • After throwing up or having diarrhea, immediately clean and disinfect contaminated surfaces by using a solution made with chlorine bleach and water:

Disinfecting against Norovirus with Chlorine Bleach

Disinfection Scenario Regular Household Bleach Dilution Cleanup and Disinfection Directions
1Hard surfaces such as non-porous floors, counter-tops, sinks, toilets 5 tablespoons of bleach in 1 gallon of water
(1000 ppm)

CLEAN-UP: Wearing gloves and other protective clothing, wipe up any vomitus or stool with paper towels and dispose in a plastic trash bag. Rinse hard surfaces with water; use kitty litter or other absorbent substance on carpeted areas to absorb liquid.
DISINFECTION: Apply bleach solution to affected area and allow to remain wet for 10 minutes. Allow to air dry. Rinse with clean water if food preparation area. Remove gloves and discard in plastic bag. Wash hands with soap and water or use an alcohol hand gel immediately after removing gloves.

2Porous surfaces, including wooden floors 1 2/3 cup bleach in 1 gallon of water (5000 ppm)
2Routine disinfection of stainless steel food/mouth contact items; toys 1 tablespoon bleach in 1 gallon water (200 ppm) Clean object first and then apply disinfectant solution. Allow to air dry.
  • Immediately remove and wash clothing or linens that may be contaminated with vomit or stool. Handle soiled items carefully—without agitating them—to avoid spreading the virus. If available, wear rubber or disposable gloves while handling soiled clothing or linens and wash hands after handling. Soiled items should be washed with detergent at the maximum available cycle length and then machine dried.

Joan Rose, PhD, is the Homer Nowlin Chair in Water Research at Michigan State University and a member of the Water Quality and Health Council.


1http://emergency.cdc.gov/disasters/disease/pdf/diarrhea-evac.pdf
2http://health.utah.gov/epi/diseases/norovirus/Guidelines_for_Environmental_Cleaning_125846_7.pdf