Stomach bug symptoms to know as norovirus cases are surging in the U.S.
Cases of norovirus, a wretched and highly contagious stomach bug, are surging in parts of the United States this winter, according to government data.
A new strain of norovirus, called GII.17[P17] now makes up a majority of outbreaks nationwide, according to data from the Centers for Disease Control and Prevention. Samples from patients in nearly 7 in 10 norovirus outbreaks have tested positive for the new strain so far this season, according to data from a network of public health laboratories called CaliciNet.
Previous numbers from the CDC showed there were 91 outbreaks of norovirus reported during the week of Dec. 5, up from 69 outbreaks the last week of November. Numbers from the past few years show a maximum of 65 outbreaks reported during that first week of December.
"We typically do see an increase in norovirus cases in the winter, around this time of year, because of large gatherings, people traveling, different generations of people together," Dr. Céline Gounder, CBS News medical contributor and editor-at-large for public health at KFF Health News, said on "CBS Mornings."
Here's what else to know.
What is the norovirus stomach bug?
Norovirus virus is a "highly infectious virus causing diarrhea, abdominal pain and vomiting," Gounder said.
Outbreaks are often seen on cruise ships, in congregate living situations like nursing homes and jails, as well as schools and places where people are close together. Earlier this month, hundreds of cruise passengers fell ill with norovirus on three different ships, according to the CDC, which recorded outbreaks of the virus on 14 cruises overall this year. December has so far seen the highest number of cruise ship outbreaks in the span of a month compared with any other month in 2024.
Cases are ticking up on land, too. The Minnesota Department of Health recently logged 40 cases of norovirus, which is twice the usual number for December, CBS News Minnesota reported.
Norovirus stomach bug symptoms
Along with vomiting, stomach pain and diarrhea, common symptoms include nausea, body aches, headache and fever.
Most norovirus outbreaks occur when people who are already infected spread the virus to others by direct means, such as through sharing food or eating utensils. Outbreaks can also be spread through food, water or contaminated surfaces.
"The most important thing you can do to prevent transmission is wash your hands. If you're sick, don't be preparing food for other people and don't be sharing food with other people," Gounder said.
People of all ages can get infected and fall sick from norovirus. Young children, older people and those with weakened immune systems are most at risk, with dehydration from vomiting and diarrhea the top concern.
How long does norovirus last?
Illness caused by norovirus typically starts suddenly, with symptoms developing 12 to 48 hours following exposure to the virus. Most people get better within one to three days and recover fully.
How long is norovirus contagious?
People can still spread the virus to others for days after they've recovered, and the virus can survive on surfaces and continue to infect people for weeks.
"You can still spread norovirus for 2 weeks or more after you feel better," the CDC website states.
What wipes kill norovirus?
To disinfect surfaces, the CDC advises using a "chlorine bleach solution with a concentration of 1,000 to 5,000 ppm (5 to 25 tablespoons of household bleach [5% to 8%] per gallon of water) or use an EPA-registered disinfecting product against norovirus."
Leave the disinfectant on the area for at least 5 minutes, the CDC states.
To keep hands clean, the CDC says not to rely solely on hand sanitizer.
"You can use hand sanitizers in addition to hand washing, but hand sanitizer is not a substitute for handwashing, which is best," the agency states, adding handwashing should last for at least 20 seconds with soap and water.
Can you test for norovirus?
A healthcare provider can typically diagnose norovirus based on symptoms but tests are also available.
"Testing usually isn't necessary, but a provider may test a stool sample to confirm your diagnosis," the Cleveland Clinic's website notes.
While at-home testing kits may exist, the CDC does not highlight them as a testing method on its website. Additionally, the Cleveland Clinic says tests usually aren't necessary unless you have an underlying condition that "affects the performance of your immune system and your ability to fight infections."
Norovirus treatment
There is no medication to treat norovirus. Rehydration is recommended by drinking water and other liquids (but not coffee, tea or alcohol).
"The key is to stay hydrated — especially little infants (and) the elderly may have trouble keeping up with that — so that is the key to treating them," Gounder said.
Anyone suffering from dehydration should seek medical help. Symptoms of dehydration include a decrease in urination, dry mouth and throat, and feeling dizzy when standing. Dehydrated children may be unusually sleepy or fussy and cry with few or no tears.
Getting lots of rest and eating soft, bland foods can also help relieve symptoms, according to the Cleveland Clinic.
How to prevent the stomach bug
Norovirus is the leading cause of foodborne illness in the United States, responsible for 58% of such infections acquired in the country each year, according to the CDC.
Rigorous and frequent handwashing is the best defense against norovirus during the peak winter season, scrubbing hands with soap and warm water for 20 seconds before meals.
Dr. Leana Wen, the former health commissioner in Baltimore, shared some best practices for people to protect themselves against the disease on "Face the Nation with Margaret Brennan" Sunday.
"Wash your hands really well, especially if you're going to buffets. Wash your hands if you're touching commonly touched surfaces, before you touch your mouth, before you touch your nose," said Wen. "Norovirus is the most common foodborne illness here in the U.S. It's very hard to avoid once it's in your family."
Cleaning surfaces with a chlorine bleach solution can also help reduce the risk of spreading the virus.
Norovirus infections are caused by a group of viruses that spread easily, with as few as 10 viral particles having the ability to make someone sick, health experts say.
There are about 2,500 norovirus outbreaks reported annually in the United States, affecting millions of people. The outbreaks can occur throughout the year but are most common from November to April.
With 19 million to 21 million illnesses each year in the United States, norovirus causes on average 900 deaths and 109,000 hospitalizations annually, mostly among adults aged 65 and older. It also leads to 465,000 emergency department visits, mostly involving young children.
