What is norovirus?

Norovirus is a very contagious virus that causes vomiting and diarrhea. It is the most common cause of acute gastroenteritis in the United States (CDPH). Norovirus is also known as the “stomach bug” or “stomach flu,” but it is not related to flu viruses, which mainly cause respiratory illnesses. Anyone can get infected with norovirus, but older adults (65 years and older), young children (under 5 years old), and immunocompromised people are at higher risk for serious illness or death.

How is norovirus spread?

Norovirus lives in the stool or vomit of infected people.

You can get norovirus from:

  • Having direct contact with an infected person (for example, when caring for them or sharing food or utensils with them).
  • Eating food or drinking liquids that are contaminated with norovirus.
  • Touching objects that are contaminated with norovirus and then putting your unwashed hands in your mouth.

Because the amount of norovirus needed to infect a person is so small, people can very easily become sick from touching food, drinks, and surfaces contaminated with norovirus. Contamination can happen through direct contact with hands or surfaces that are contaminated with stool or vomit, or by tiny droplets from nearby vomit that can travel through the air.

What are the symptoms of norovirus?

Symptoms of norovirus are nausea, vomiting, stomach pain, and/or diarrhea. Some people also experience headache, fever, chills, and muscle aches. Symptoms usually last for 1 to 3 days. However, during that period, people can feel very ill and vomit many times a day, sometimes violently and without warning.

How soon after exposure to norovirus will symptoms appear?

Symptoms usually begin 12 to 48 hours after exposure to the virus.

How can you help prevent the spread of norovirus?

If you think you have norovirus, stay home until you have been symptom-free for 48 hours without the use of medication. Stay away from others and clean shared surfaces often.

What is the treatment for norovirus?

There is no specific treatment for norovirus. A person with norovirus should drink plenty of fluids to replace fluids lost from vomiting and diarrhea and prevent dehydration. This is especially important for people who are very young, very old, or immunocompromised. If you think you or someone you are caring for is becoming severely dehydrated, contact your healthcare provider or go to the nearest emergency room.

How can I prevent the spread of norovirus?

Hand washing with soap and water is the most important way to prevent the spread of norovirus. Alcohol-based sanitizers are not as effective as washing hands with soap and water.

Thorough cleaning and disinfecting is also important:

  • Any surfaces near vomit or diarrhea should be promptly cleaned and disinfected with bleach solution and then rinsed.
  • Throw out any food items that may have become contaminated with norovirus.
  • Any linens (for example, clothes, towels, tablecloths) that have been soiled to any extent with vomit or stool should be promptly washed in hot water.

For more information on cleaning and disinfection for norovirus, see the Water Quality and Health Council’s Norovirus Cleaning Instructions (English | Español) or watch the video below:

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Norovirus Data for Santa Clara County

The CDC’s WastewaterSCAN Dashboard includes data on the amount of norovirus found in samples collected at wastewater facilities that serve people in Santa Clara County.

Four wastewater treatment facilities receive wastewater from designated geographic areas called “sewersheds” in Santa Clara County:

  • San Jose Sewershed
  • Palo Alto Sewershed
  • Sunnyvale Sewershed
  • Gilroy Sewershed

What does the Public Health Department do about norovirus?

The Public Health Department investigates all outbreaks of norovirus reported by a health care provider or school.

Additional Resources

  • Norovirus (Centers for Disease Control and Prevention)
  • Norovirus (California Department of Public Health)

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