Health
Norovirus Surges Across the U.S. This Winter
Health Points
- Norovirus cases are rising, with higher levels in the Midwest and Northeast.
- A new GII.17 variant is driving more outbreaks, mostly among people without existing immunity.
- Symptoms often start suddenly and include vomiting, diarrhea, and stomach cramps.
Norovirus, sometimes called the “winter vomiting disease,” is making a comeback across the country as the holiday season approaches. Levels in wastewater have increased by 45% since November, signaling a challenging winter in many regions.
This highly contagious stomach virus is causing school closures and more outbreaks on cruise ships, hitting hardest in the Midwest and Northeast. Wastewater data reveals this upward trend began in October and continues to rise.
Norovirus Surge
“We’re seeing upticks in norovirus across the system, but that’s not out of the ordinary. … It’s historically a winter bug,” says Dr. Scott Roberts of Yale School of Medicine.
Most outbreaks happen from November to April, and places like schools and nursing homes are especially at risk. Labs report positivity rates above 12% for mid-December, and WastewaterSCAN’s data shows numbers are rising faster than last year.
Still, experts note that the current number of outbreaks is within the average range for the season so far. As Dr. Roberts explains, “So far, we’re not yet to the level that we were at last year, which was really our worst year since pre-COVID … but it’s certainly going up.”
He adds, “Time will tell how bad it will get. Now is the time to be vigilant. I expect things to get worse before they get better.”
Norovirus GII.17 Variant
For years, most norovirus outbreaks were linked to the GII.4 strain. However, a newer variant called GII.17 has grown sharply, especially during this year’s season.
According to a recent CDC study, GII.17 is now behind 75% of outbreaks in the U.S., up from less than 10% last year. Dr. Roberts notes, “Whenever there is a new strain, it’s really easy for it to start spreading rapidly, and that’s what we saw last year.”
More people may get sick this winter because fewer have immunity to GII.17. Dr. William Schaffner from Vanderbilt University Medical Center says norovirus can provide some immunity, but it may not protect you from new strains.
Roberts points out, “We don’t have a good sense of how long this immunity can actually protect us … but that immunity probably won’t protect you against another strain.”
Norovirus Symptoms
Symptoms typically show up swiftly, within 12–48 hours after exposure. The virus is well known for its sudden and unpleasant onset.
Common signs include vomiting, diarrhea, nausea, and stomach pain, with headaches and mild fevers appearing less often. Dr. Schaffner reassures, “Fortunately, it’s relatively brief. You’re miserable for about 48 hours, then you get better.” Most people recover within one to three days.
Stay informed, be extra cautious as gatherings increase, and practice good hygiene to reduce your risk of infection this season.
