While flu season is winding down, health officials are keeping a close eye on another illness making its way across much of the United States: norovirus. Often referred to as the “winter vomiting disease,” the highly contagious stomach virus is showing elevated levels nationwide, according to recent wastewater surveillance data.
Recent outbreaks have been reported among hikers along California’s Pacific Crest Trail, but experts say the increase is not limited to outdoor enthusiasts. Wastewater monitoring indicates widespread circulation of the virus across many regions of the country, particularly in the Northeast. Despite the recent rise, health experts note that current outbreak numbers remain within the range typically seen during norovirus season.
One factor contributing to the virus’s spread is the emergence of a newer strain known as GII.17. This variant has become the dominant strain in the United States, accounting for roughly three-quarters of outbreaks during the 2024-25 season. Although it does not appear to be more severe or inherently more contagious than previous strains, fewer people have built immunity against it, allowing it to spread more easily.
Experts also point to increased travel and warmer temperatures as factors driving transmission. Holiday gatherings, crowded indoor environments, cruise ships, and other group settings create ideal conditions for the virus to spread rapidly. Norovirus is considered one of the most contagious illnesses, with infected individuals capable of passing it to several others.
Symptoms typically appear within one to two days of exposure and include intense vomiting, diarrhea, stomach cramps, and nausea. Most healthy adults recover within a few days, but dehydration can become a serious concern, especially for young children and older adults.
Because there is no specific treatment for norovirus, prevention remains critical. Health officials recommend frequent handwashing with soap and water, avoiding raw shellfish, disinfecting contaminated surfaces, and staying home when sick to help limit the virus’s spread.
