Noroviruses, also known as winter vomiting bugs, are a common cause of sickness and diarrhea (gastroenteritis).
According to the Centers for Disease Control and Prevention (CDC), noroviruses cause 19-21 million infections, 56,000-71,000 hospitalizations, and 570-800 deaths every year in the United States.
Although noroviruses more commonly strike during the winter months, they can appear at any time of the year.
Norovirus infection is sometimes misnamed “stomach flu.” The medical term is gastroenteritis, and it is not associated with flu, a respiratory infection.
Fast facts on norovirus
Here are some key points about norovirus. More detail and supporting information is in the main article.
Around 90 percent of non-bacterial cases of gastroenteritis worldwide are believed to be caused by noroviruses.
Although known as the winter vomiting bug, norovirus can strike at any time of year.
Norovirus outbreaks are more likely to occur in crowded or closed communities.
The most common cause of norovirus is believed to be contaminated food.
Simple measures of personal and food hygiene can substantially reduce norovirus transmission.
What is norovirus?
The majority of non-bacterial outbreaks of gastroenteritis are attributable to noroviruses.
Noroviruses include Norwalk, Snow Mountain, and Hawaii viruses. Approximately 90 percent of all non-bacterial outbreaks of gastroenteritis are believed to be caused by noroviruses globally.
Noroviruses are shed in the feces (stools) and vomit of infected people and animals.
The infection can be transmitted by:
consuming contaminated foods
drinking contaminated water
touching an infected person with your hand and then touching your mouth
touching a contaminated surface with your hand and then touching your mouth
It is not easy to eliminate noroviruses because they can survive in both hot and cold temperatures, and are resistant to many disinfectants.
As noroviruses undergo genetic changes all the time, humans tend to become infected more than once during their lifetimes. Normally, if you have recurring infections, symptoms are less severe each time.
Norovirus infection outbreaks are more likely to occur in crowded or closed communities, such as cruise ships, long-term care facilities, prisons, overnight camps, and dormitories – places where the virus can spread rapidly from human to human.
Nausea, vomiting and abdominal pain are typical symptoms of norovirus infection.
Typical symptoms include:
nausea, usually the first symptom
vomiting, sometimes violent and sudden
stomachache and abdominal pain
watery or loose diarrhea
feeling unwell and lethargic (malaise)
fever and chills, usually mild
myalgias, or body aches
During the brief period when symptoms are present people can feel very ill and vomit, often violently without warning, many times a day.
Signs and symptoms, which usually last from 1-3 days, appear about 24-48 hours after initial infection – in some cases, the incubation period may only be 12 hours. Sometimes, the diarrhea can last longer than 3 days.
According to the Centers for Disease Control and Prevention (CDC), the virus can be in the stool and vomit of an infected person from the day they start to feel ill to as long as 2 weeks after they feel better.
Treatments and risk factors
No specific therapy exists for norovirus gastroenteritis, so management is primarily to prevent dehydration and provide symptom control.
Experts say that fasting will not speed up recovery. Therefore, patients should eat a light diet with foods that are easy to digest, such as rice, bread, soups, or pasta. Babies should be given what they would usually eat.
It is important to replace the fluids that are lost through vomiting or diarrhea, especially with very young children and elderly people.
The speed of dehydration can be sudden and in some cases life-threatening. Young children and elderly patients are particularly susceptible to dehydration, which means dehydration is an important component to look out for, because the symptoms occur so abruptly. Patients who are not able to drink enough liquids may need to receive fluids intravenously.