Norovirus Tracker 2026
US Activity by State
14 states participate in CDC NoroSTAT. All others shown but have no formal cluster surveillance data. National wastewater monitoring (CDC NWSS) covers all 50 states.
CDC NoroSTAT tracks outbreak clusters (2+ linked cases) from 14 state health departments. Only the 14-state season aggregate is published publicly. Wastewater data from CDC NWSS is independent of NoroSTAT and covers all 50 states.
Sources: CDC NoroSTAT · CDC CaliciNet · CDC NWSS · WastewaterSCAN. Not a medical authority. Verify with CDC.
About Norovirus
What is norovirus?
Norovirus is the leading cause of stomach illness in the United States. You have almost certainly had it at some point. It is sometimes called the "stomach flu," but it has nothing to do with the flu virus. Each year it causes about 21 million illnesses, 109,000 hospitalizations, and an estimated 570 to 800 deaths in the US, mostly in elderly adults. It spreads extremely easily and is found everywhere in the world.
How does it spread?
Norovirus is one of the most contagious viruses known. It takes fewer than 20 virus particles to make a person sick, yet an infected person can shed billions of particles. It spreads through eating or drinking contaminated food or water, touching surfaces that have the virus on them and then touching your mouth, and close contact with someone who is infected. When a sick person vomits, tiny invisible droplets can spread through the air and land on nearby surfaces. The virus can survive on hard surfaces for weeks, and regular cleaning sprays often do not kill it.
What are the symptoms?
Symptoms come on fast. They usually start 12 to 48 hours after contact with the virus. They include sudden nausea, vomiting, diarrhea, and stomach cramping. Some people also get a mild fever, headache, or body aches. Most people feel better within 1 to 3 days. The main danger is dehydration, especially in young children and older adults. Signs of dehydration include very little urination, dry mouth, and dizziness.
You stay contagious after you feel better.
This is the part most people do not know. You can spread norovirus to others while you are sick and for at least 2 full days after your symptoms stop. Some people shed the virus for up to 2 weeks with no symptoms at all. This is why norovirus rips through households, schools, cruise ships, and nursing homes so quickly. People return to normal life before they stop being contagious.
Who is most at risk of serious illness?
While anyone can get norovirus, children under 5, adults over 65, and people with weakened immune systems are most likely to become severely dehydrated and need hospital care. Norovirus is the most common cause of gastroenteritis outbreaks in nursing homes, where it can be life-threatening for residents.
Why is it elevated in 2026?
Norovirus season normally peaks between November and April and quiets down in late spring and summer. The fact that wastewater surveillance is still detecting it at elevated levels heading into June 2026 is unusual. Scientists believe this is partly driven by the dominant strain this season, GII.4 Sydney, which has historically caused larger and longer outbreaks than other strains. GII.4 strains drove the major norovirus waves of 2006–07 and 2012–13. Its return to dominance after the GII.17 strain dominated last season is likely contributing to the extended activity.
Sources: CDC About Norovirus · CDC Norovirus Prevention · WHO Disease Fact Sheets · CDC Yellow Book 2026: Norovirus