Your Norovirus Questions, Answered

Aron J. Hall, DVM, MSPH


April 11, 2019

Editorial Collaboration

Medscape &

This season's norovirus outbreaks have closed schools and forced cruise ships back to port. Here, Centers for Disease Control and Prevention (CDC) norovirus experts answer common questions about how to prevent and manage this highly contagious illness.

How Common Is Norovirus Illness?

Norovirus is a leading cause of vomiting and diarrhea from acute gastroenteritis across all age groups, from infants to the elderly. Each year, approximately 20 million people in the United States will have acute gastroenteritis caused by norovirus, including about 2 million who are cared for in outpatient clinics, emergency departments, or inpatient hospital settings. Norovirus infections and outbreaks can occur at any time of the year but are most common from November through April. Typical settings for norovirus outbreaks are acute and long-term care facilities, which may house many individuals at risk for severe norovirus infections. Schools and daycares are also common settings for norovirus outbreaks.

Who Is at Higher Risk for Severe Norovirus Illness?

Some patient groups, such as infants and children under age 2 years, adults aged 65 years or older, and people who are immunocompromised, are at higher risk for severe norovirus illness. Although most cases of norovirus illness are self-limited, dehydration is the most common complication, which often leads to emergency department visits, hospitalizations, and even deaths. Prolonged infections with symptoms lasting for several days or even weeks can also occur among these high-risk groups.

How Can Patients Protect Against Norovirus Infections?

Norovirus is primarily transmitted is by direct person-to-person contact, particularly when an infected person touches and contaminates food, water, or environmental surfaces. Therefore, handwashing with soap and water is the first line of defense against norovirus. Remind patients that they should wash their hands frequently and thoroughly, especially after using the bathroom and changing diapers, and always before handling, preparing, or eating food. Alcohol-based hand sanitizers are generally not effective at killing norovirus. To ensure that norovirus is removed from hands, thorough handwashing with soap and water for at least 20 seconds is important. Alcohol-based hand sanitizers can be used in addition to handwashing, but not as a substitute for washing with soap and water.

In addition to washing hands, it is important for patients to take the following specific steps to prevent norovirus from spreading in their households:

  • If a family member is vomiting or has diarrhea, that person should not take care of other people or prepare food for others; and

  • After a vomiting or diarrhea incident in the household, immediately and thoroughly clean and disinfect all surfaces with a bleach-based household cleaner. Wash all soiled linens and clothing with hot water at the maximum cycle length and machine dry at highest heat setting.

If Norovirus Is Suspected, What Testing Should Be Done?

You may decide that testing for norovirus is necessary during a suspected outbreak, or when a patient has prolonged or severe symptoms. Whole stool is the preferred clinical specimen to detect norovirus, but the virus can also be detected in vomitus samples and rectal swabs. Ideally, you should collect stool specimens within 48-72 hours after the patient starts having symptoms. Diagnostic tests are available at all public health laboratories and increasingly at many clinical laboratories; most use highly sensitive real-time reverse transcription-polymerase chain reaction (RT-qPCR) assays to detect norovirus ribonucleic acid (RNA). In addition, several multipathogen panel tests are now commercially available that combine norovirus with other common bacterial and parasitic pathogens.

See this page for more information about specimen collection and laboratory diagnosis.

How Is Norovirus Illness Treated?

There are no antiviral therapies for patients who have norovirus illness. The recommended management is similar to that for other causes of viral gastroenteritis, including prevention and treatment of dehydration. It is important to watch for dehydration in infants, young children, and the elderly, and help prevent severe illness by starting rehydration therapy as soon as needed. Most patients will benefit from oral rehydration therapy. In cases of moderate to severe dehydration, intravenous fluids may be warranted. If a patient has frequent vomiting with dehydration, antiemetics may also play a role in supportive therapy, depending on the age of the patient and severity of symptoms.

In healthcare settings and long-term care facilities, protecting patients from norovirus infection requires standard infection prevention measures. This includes practicing proper hand hygiene and avoiding patient care when you have gastroenteritis and for 48 hours after you recover. Remind visitors to practice proper handwashing with soap and water, and exclude visitors with gastroenteritis.

How Should Outbreaks Be Handled and Reported?

Individual cases of norovirus are not nationally notifiable. However, outbreaks are reportable in all states, so if you suspect a norovirus outbreak, notify your local health department, which can provide further assistance with diagnostic testing and outbreak management.

During outbreaks in healthcare settings and long-term care facilities, you should do the following:

  • In addition to thorough handwashing with soap and water, use gowns and gloves when touching or caring for patients with norovirus illness;

  • Routinely clean and disinfect all high-touch patient surfaces and equipment; and

  • Ensure that contaminated clothing or linens are removed and washed.

You should quickly identify patients who might have norovirus infection. Patients who have symptoms may be placed in private rooms, or they can share rooms with other patients with norovirus infection.

Pay close attention to the most vulnerable patients in long-term care facilities who are at highest risk for severe norovirus illness and may require earlier transport to the hospital.

When Might a Norovirus Vaccine Become Available?

Multiple vaccines are in development for norovirus. CDC plays an important role in conducting surveillance that helps to better understand the burden of norovirus illness and who might benefit most from interventions. CDC also conducts studies to understand norovirus strains, duration of immunity, and symptom expression to help determine best practices for potential vaccines. Finally, CDC is working to identify potential target groups for norovirus vaccines, such as young children, the elderly, food workers, and healthcare workers.

For more information on norovirus prevention, diagnosis, and management, see the following resources:

CDC has also developed a poster on norovirus for healthcare providers and staff who may be involved in norovirus prevention and control.