How Norovirus Spreads
Norovirus spreads very easily and quickly in different ways.
You can get norovirus by accidentally getting tiny particles of feces (poop) or vomit from an infected person in your mouth.
This can happen if you
- eat food or drink liquids that are contaminated with norovirus,
- touch surfaces or objects contaminated with norovirus and then put your fingers in your mouth, or
- have direct contact with someone who is infected with norovirus, such as by caring for them or sharing food or eating utensils with them.
If you get norovirus illness, you can shed billions of norovirus particles that you can’t see without a microscope. Only a few norovirus particles can make other people sick. You are most contagious
- when you have symptoms of norovirus illness, especially vomiting, and
- during the first few days after you recover from norovirus illness.
However, studies have shown that you can still spread norovirus for two weeks or more after you feel better.
Norovirus can easily contaminate food and water because it only takes a very small amount of virus particles to make you sick. Food and water can get contaminated with norovirus in many ways, including when:
- An infected person touches food with their bare hands that have feces (poop) or vomit particles on them
- Food is placed on a counter or surface that has feces or vomit particles on it
- Tiny drops of vomit from an infected person spray through the air and land on the food
- The food is grown or harvested with contaminated water, such as oysters harvested from contaminated water, or fruit and vegetables irrigated with contaminated water in the field
Norovirus is the leading cause of illness and outbreaks from contaminated food in the United States. Most of these outbreaks occur in food service settings like restaurants. Infected food workers are frequently the source of outbreaks, often by touching ready-to-eat foods, such as raw fruits and vegetables, with their bare hands before serving them. However, any food served raw or handled after being cooked can become contaminated with norovirus.
- At the source such as when a septic tank leaks into a well
- When an infected person vomits or poops in the water
- When water isn’t treated properly, such as with not enough chlorine
For more information on healthy water and how water can get contaminated, visit www.cdc.gov/healthywater/.
- An infected person touches the surface with their bare hands that have feces or vomit particles on them
- An infected person vomits or has diarrhea that splatters onto surfaces
- Food, water, or objects that are contaminated with norovirus are placed on surfaces
- Tiny particles of vomit spray through the air and land on surfaces or enter a person’s mouth, then he or she swallows it