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Causes

These viruses are highly contagious. They are spread by fecal to oral contamination of water and food.

Infection can occur as a result of contaminated:

• Municipal water supplies, recreational lakes, swimming pools, wells, water stored on cruise ships, among other sources
• Raw (or improperly steamed) shellfish, especially clams and oysters
• Food and drinks (due to infected food handlers who either do not wash their hands or wash their hands improperly after using the bathroom)
• Surfaces (eg, touching a door knob and then placing hands in mouth)

The viruses can also spread by direct contact with an ill person. This is common in a daycare center or nursing home.

Risk Factors

The following factors increase your chance of developing noroviruses:

• Age: more common in adults and children than the very young
• Being exposed to a contaminated water supply (eg, recreational lake)
• Consuming contaminated foods or liquids
• Touching contaminated surfaces
• Taking care of someone who is infected with the virus (eg, in a nursing home or daycare center)
  • Note: A person is contagious from the start of symptoms to at least three days after recovery. Sometimes it can be up to three weeks.

Even if you have been infected with norovirus in the past, you can become ill again if:

• It is a different strain
• It is over 24 months since your last exposure

Hope this helps,

Rosa