Norovirus Infection

Swine Flu FAQ Slideshow

Medical Reviewing Editor: Frederick Hecht, MD, FAAP, FACMG

• What are noroviruses?
• What are the symptoms of illness caused by noroviruses?
• What is the name of the illness caused by noroviruses?
• How serious is a norovirus disease?
• How do people become infected with noroviruses?
• When do symptoms appear?
• Are noroviruses contagious?
• Who gets norovirus infection?
• What treatment is available for people with norovirus infection?
• Can norovirus infection be prevented?

Norovirus Infection: A Cause for Travelers' Concern? Medical Author: Melissa Conrad Stöppler, MD Medical Editor: William C. Shiel Jr., MD, FACP, FACR A reported outbreak of norovirus infection on a cruise ship has left many would-be travelers worried about contracting the illness and wondering if they can prevent it. Many people may not be familiar with the term norovirus, but it's actually a relatively new term for an old disease. The many strains of noroviruses cause a self-limited gastrointestinal illness that many refer to as the "stomach flu." Outbreaks of norovirus infection have also been documented as coming from restaurants, schools, and nursing homes. Norovirus is now the official name for the group of viruses that, for a time, were referred to as "Norwalk-like" viruses, after the original strain "Norwalk virus," which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968. Other names for this group of viruses have included caliciviruses (the virus family name) and small round structured viruses (SRSVs). After infection with one of the noroviruses, symptoms typically appear within one to two days. The sudden onset of nausea and vomiting, watery diarrhea, and abdominal cramping are the most common symptoms of norovirus infection. A low-grade fever may be present. The illness typically resolves on its own within 24 to 60 hours without serious long-term effects. However, dehydration is a potential complication, especially among children and the elderly, possibly requiring medical treatment. Learn about the transmission of norovirus infection » Top Searched Norovirus Infection Terms: gastroenteritis, treatment, transmission, where does it come from, cruise ships, prevention, stomach flu

What are noroviruses?

Noroviruses are a group of viruses that cause the "stomach flu," or gastroenteritis (GAS-tro-en-ter-I-tis), in people. The term norovirus was recently approved as the official name for this group of viruses. Several other names have been used for noroviruses, including:

• Norwalk-like viruses (NLVs)



• caliciviruses (because they belong to the virus family Caliciviridae)



• small round structured viruses.

Viruses are very different from bacteria and parasites, some of which can cause illnesses similar to norovirus infection. Like all viral infections, noroviruses are not affected by treatment with antibiotics, and cannot grow outside of a person's body.

What are the symptoms of illness caused by noroviruses?

Norovirus infection usually starts suddenly. The infected person often feels very sick with nausea and vomiting and watery non-bloody diarrhea with stomach cramps. Vomiting is more common in children than adults. Sometimes there is a low-grade fever. There may also be chills, headache, muscle aches, and a general sense of tiredness.

Studies with volunteers have shown that as many as 30% of norovirus infections may be asymptomatic. These people are infected with the virus but have no symptoms (asymptomatic). The role of asymptomatic infection in the transmission of norovirus is not well understood. It is possible that people who seem well can transmit the virus.

What is the name of the illness caused by noroviruses?

Illness caused by norovirus infection has several names, including:

• stomach flu—this "stomach flu" is not related to the flu (or influenza), which is a respiratory illness caused by influenza virus.



• viral gastroenteritis—the most common name for illness caused by norovirus. Gastroenteritis refers to an inflammation of the stomach and intestines.



• acute gastroenteritis



• non-bacterial gastroenteritis



• food poisoning (although there are other causes of food poisoning)



• calicivirus infection

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