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Norovirus, often called the “winter vomiting disease,” is spreading rapidly across the United States, with cases sharply rising as summer begins. According to data from WastewaterSCAN, norovirus concentrations are now “high” nationwide, with the sharpest increases seen in the Midwest and Northeast. Levels have climbed 45% since November, and experts say a new virus variant is likely fueling the surge.
Norovirus is a highly contagious virus that causes sudden vomiting, diarrhea, stomach cramps, and sometimes fever or headache. The virus spreads easily through close contact, contaminated food or surfaces, and especially through improper handwashing. Just a few virus particles—sometimes as few as ten—are enough to make someone sick. People are most contagious from the start of symptoms until at least a few days after feeling better, but can continue to shed the virus for up to two weeks.
Symptoms usually begin 12–48 hours after exposure and last one to three days. Most people recover without medical care, but dehydration is a risk, especially for young children and older adults.
The Centers for Disease Control and Prevention (CDC) estimates that each year, norovirus causes between 19 and 21 million illnesses, more than 100,000 hospitalizations, and about 900 deaths in the United States. Outbreaks are being reported in schools, daycares, nursing homes, and cruise ships, with recent school closures in Massachusetts due to suspected norovirus clusters.
Most norovirus outbreaks typically happen from November to April, but experts from the CDC warn that the current increase started earlier than usual and is being driven by a newer variant, GII.17, which accounted for 75% of outbreaks during the 2024–2025 season. Because immunity to norovirus is only partial and short-lived, people can get infected more than once and with different strains.
There is no specific treatment for norovirus. The main advice is to rest and drink fluids in small, frequent amounts to prevent dehydration. In some cases, intravenous fluids are needed.
Prevention is challenging because norovirus is resistant to alcohol-based hand sanitizers and many common cleaners. Washing soiled clothes and linens in hot water, avoiding food preparation while sick, and cleaning frequently touched surfaces are also recommended.
Currently, there is no vaccine available for norovirus, though a candidate vaccine is in phase 3 clinical trials.