Noroviruses are very contagious and hardy viruses that cause severe stomach upsets (gastroenteritis). Find out how norovirus can make you ill and how to avoid infection.


People get sick suddenly, usually within a day. Symptoms include:

  • diarrhoea
  • violent vomiting (often projectile)
  • stomach cramps
  • mild fever
  • chills
  • headache
  • muscle aches
  • tiredness
  • nausea.

Keeping up fluid intake during this time is important because of the risk of dehydration. The illness only lasts a few days and does not usually cause any complications.

How you can be exposed

Noroviruses are a group of very contagious and hardy viruses that cause severe stomach upsets (gastroenteritis) in people. You can be infected with a norovirus after eating contaminated food, and can pass the virus on to others through cross-contamination of food and other surfaces. For example, norovirus may be present in ice, sewage-contaminated produce, or oysters harvested from areas where there is untreated sewage.

In New Zealand, commercial shellfish are collected under regulations that prevent harvest from polluted water. Take care when preparing recreationally-collected shellfish as these are not produced under regulated conditions.

How you can avoid infection

  • Check for warning signs if collecting shellfish, and don't collect shellfish near sewage outlets.
  • If possible, cook recreationally collected shellfish thoroughly before eating. Boil for 3 to 5 minutes (3 minutes if shelled), or steam for 4 to 9 minutes. Internal temperature must reach 90 degrees Celsius for 90 seconds to kill virus particles.
  • Wash all fruits and vegetables thoroughly, and cook food well, especially if someone at your house is sick.
  • If you're showing symptoms of a norovirus infection, don't prepare food while ill, and for at least 3 days afterwards.
  • Clean hands, surfaces, and utensils thoroughly. Wipe all surfaces including handles with bleach-based household cleaner (follow manufacturer's instructions).

If you are caring for someone who is sick:

  • Keep the toilet area and all bathroom surfaces (toilet, taps, handles) clean using household disinfectant. These are significant sources of infection.
  • Remove and wash any furnishings, including bedding that may be contaminated, using soap and hot water. Viral particles can survive for at least 12 days on some surfaces.

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