Nationwide Rise in Wastewater Signals Early Season
A highly contagious gastrointestinal virus is spreading quickly across the United States ahead of the holiday season, with new data showing a sharp rise in norovirus activity. Often called the winter vomiting disease, norovirus levels have climbed 69 percent nationwide since mid October, according to WastewaterSCAN, a program run by Stanford University and Emory University.
Scientific program manager Amanda Bidwell said the country is now in the high category for norovirus circulation. Rates are highest in the Northeast and Midwest, with Louisiana, Michigan and Indiana showing significant increases. Wastewater trends indicate infections are rising earlier than usual this year.
Shifting Variants and Earlier Seasonal Peaks
For decades, norovirus outbreaks were primarily driven by the strain GII.4, but last year the variant GII.17 accounted for roughly 75 percent of outbreaks. Experts say the rise of GII.17 may help explain why seasonal spikes in 2024 and 2025 began in October rather than winter.
Dr. Robert Atmar of Baylor College of Medicine noted that either increased virus transmissibility or lower immunity in the population could be driving GII.17’s dominance. Dr. Craig Wilen of Yale University added that many people simply have less immunity to GII.17 compared to older variants. Researchers say it is unclear which strain will dominate this year, but they expect some protection from last year’s widespread infections.
Symptoms and Transmission
Norovirus causes around 20 million cases in the United States each year and is responsible for more than half of all foodborne illnesses. It spreads easily through contact with infected people, contaminated surfaces or contaminated food and water. The virus can remain infectious for more than two weeks, even after symptoms fade.
Common symptoms include diarrhea, vomiting, stomach pain, fever and body aches. Illness typically begins 12 to 48 hours after exposure and lasts several days. Young children, older adults and people with weakened immune systems are more likely to face complications and may need medical attention due to dehydration.
How to Protect Yourself
Norovirus is difficult to eliminate and can survive temperatures up to 145°F. Standard alcohol based hand sanitizers are less effective, making proper cleaning essential. The CDC recommends washing hands thoroughly with soap and water, disinfecting surfaces with diluted bleach and washing contaminated clothing in hot water.
Food safety is also critical. Fruits and vegetables should be washed carefully, and shellfish such as oysters should be fully cooked. There is currently no antiviral treatment for norovirus, so staying hydrated is key. A Phase 3 Moderna vaccine trial is underway, but no vaccine is available yet.