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Norovirus

Definition

Noroviruses (previously known as Norwalk-like viruses) are a group of viruses and are the most common cause of acute gastroenteritis in the United States. The most common symptoms of a norovirus illness include nausea, vomiting, diarrhea, and stomach cramps. Illness often begins suddenly but is often brief, with symptoms usually lasting 1 to 2 days. Dehydration may result in individuals with this illness, but the disease is self-limiting and there are no long-term health effects.

Symptoms

Symptoms of norovirus illness usually begin 24 to 48 hours after ingestion of the virus, but may appear in as little as 12 hours after exposure. The illness is usually brief, lasting 1 to 2 days; however, individuals may remain contagious from the moment they become ill to three days after recovery. The most common symptoms of norovirus illness include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Stomach cramping

Sometimes, norovirus can cause a low-grade fever, chills, headache, muscle aches, and fatigue. Dehydration can also occur, which may require hospitalization. There are no long-term effects resulting from norovirus illness.

Causes

Noroviruses are very contagious. They are found in the feces and vomit of infected individuals. Norovirus illness is caused by consumption of the virus from fecally-contaminated food or water or by direct person-to-person spread. Other common sources of infection include:

  • Poorly cooked shellfish
  • Environmental contamination: touching a contaminated surface and then touching the mouth or eating without washing hands first
  • Transmission due to the aerosolization of vomit that contaminates surfaces or the ingestion of aerosolized particles in the air

Risk Factors

People with increased risk of norovirus illness include:

  • Those caring for or that are in direct contact with an infected individual
  • Children and day care providers in day care settings
  • Residents and staff of nursing homes

Prevention

  • Wash hands with warm, soapy water for 20 seconds after using the bathroom or changing diapers and before preparing or eating food. Alcohol sanitizers have not been shown to be effective for killing norovirus.
  • Immediately clean and disinfect surfaces in the household that have become contaminated with feces or vomit
  • Carefully wash fruits and vegetables, thoroughly cook oysters before consumption
  • Do not prepare food or work while ill

Treatment

Rehydration and electrolyte replacement are the main treatments for norovirus. The illness is self-limiting. Antibiotics are of no use.

Statistics

Individual norovirus infections are not reportable. However, in 2015 there were 48 outbreaks where norovirus was confirmed or suspected with over 900 people affected.

For more detailed information and statistics on all notifiable diseases, please see our current annual report located in the reports section of the CADE homepage.

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