Understanding Norovirus Outbreaks

Norovirus, a highly contagious stomach illness, tends to spread rapidly in crowded environments such as cruise ships, long-term care facilities, and schools. While anyone can become infected, young children and the elderly are particularly at risk for severe symptoms.

Norovirus impacts the stomach and intestines, leading to symptoms like diarrhea, vomiting, nausea, and stomach cramps. Additional symptoms may include fever, headaches, and body aches. After exposure, signs of illness typically begin within 12 to 48 hours.

This virus is the leading cause of gastrointestinal issues—including vomiting and diarrhea—as well as foodborne illnesses in the U.S. Every year, hundreds of thousands of individuals seek emergency care due to norovirus infections.

You can catch norovirus through close contact with someone who is infected or by touching contaminated food, water, or surfaces. The virus can also spread through contact with vomit or feces from an ill person.

Doctors often diagnose norovirus based on a person's reported symptoms, though laboratory tests can confirm the infection in clinical settings.

There is currently no specific medical treatment approved for norovirus. Healthcare providers instead focus on relieving symptoms and minimizing the risk of transmission. They may offer medications to reduce nausea and vomiting and administer fluids to combat dehydration. Diarrhea can be treated with available over-the-counter or prescription medicines.

In most healthy adults, the illness resolves within a few days. However, people with weakened immune systems may experience more severe or prolonged symptoms that could become dangerous.

At this time, no vaccines are officially available to prevent norovirus, though several are in development and undergoing human testing.

Researchers, supported by NIH funding, are investigating how the virus behaves using miniature 3D models of human intestinal tissue—referred to as "mini-guts." These allow scientists to infect the tissue with norovirus and observe how it replicates inside the cells.

“This method lets us examine how cells respond to the virus and evaluate antiviral treatments that may block the infection,” says Dr. Robert Atmar, an infectious disease specialist at Baylor College of Medicine.

Experts are also studying specific cell proteins—known as receptors—that the virus uses to invade cells. Dr. Atmar and Dr. Mary Estes, a virology researcher at Baylor, are working to identify the receptor used by a newer strain of the virus that’s currently spreading globally.

“By finding the receptor, we can better understand how the virus works and how to prevent infection,” says Dr. Estes.

If you suspect you have norovirus, medical professionals advise staying home for at least 48 hours to avoid infecting others. Limiting contact with others during this time is highly recommended. Additional guidance on prevention and care is available in the accompanying Wise Choices section.