Ready for Norovirus 2024? The stomach bug is on the rise again

Norovirus, the extremely contagious stomach bug that causes vomiting and diarrhea, is spreading and sickening millions in the United States. Cases of the nasty gastrointestinal illness, also known as the "stomach flu," continue to climb as the country enters spring.

Respiratory virus season may be coming to an end, but the 2023–2024 norovirus season is still well underway. Nationally, norovirus is circulating at the highest levels since last April, according to data from the U.S. Centers for Disease Control and Prevention.

Outbreaks are spiking in many parts of the country, including the Northeast and Midwest, and even hitting cruise ships.

Norovirus spreads easily among people in enclosed settings and tends to peak in the cooler winter months. As thousands of Americans travel this month for spring break and Easter, U.S. health officials are urging people to take steps to stop the spread.

Although norovirus is commonly called the “stomach flu,” it is not related to the flu, which is caused by influenza viruses.

Norovirus is a leading cause of acute gastroenteritis, or an inflammation of the lining of the stomach and intestines, per the CDC. This can result in intense bouts of vomiting, diarrhea, nausea and stomach cramps.

Symptoms usually begin 12 to 48 hours after exposure — these are often sudden and very unpleasant, but most people will recover on their own.

“This is the dreaded virus that leaves us in the bathroom for about a day or two, we’ve all been there,” NBC News medical contributor Dr. Tara Narula said on TODAY in a segment on Feb. 27.

Norovirus is highly contagious, and anyone can become infected. Every year in the U.S., it causes about 20 million cases of vomiting and diarrhea, 465,000 emergency room visits, 109,000 hospitalizations and 900 deaths, per the CDC.

Although norovirus can spread year-round, outbreaks are most common during the late fall, winter and early spring. As of late March, norovirus cases are still climbing in the U.S.

According to the latest data from laboratories across the country reporting to the CDC, the rate of norovirus tests coming back positive, averaged over three weeks, was just over 13.3% as of Mar. 30 — up from about 9% in mid-January.

Percent Positive
PCR Detection
Norovirus for the US (3 week average) (CDC)
Percent Positive PCR Detection Norovirus for the US (3 week average) (CDC)

Outbreaks have also been rising steadily in recent months. During Aug. 1, 2023 to Mar. 12, 2024, there were 1,020 norovirus outbreaks reported by the 15 states participating in the CDC’s NoroSTAT surveillance program. During the same period the last seasonal year, there were 789 norovirus outbreaks reported by these states.

However, total number of outbreaks reported during the 2023–2024 norovirus seasonal year is comparable to the number reported during the 2012–2020 seasonal years, according to the CDC.

“Currently, norovirus outbreak activity in the United States is within the range we would expect for this time of year and is within the range reported during the same time periods in previous years,” a spokesperson for CDC tells TODAY.com.

“We generally see an increase during winter and are continuing to monitor this," the CDC spokesperson added.

Where is norovirus spreading?

Outbreaks of norovirus are impacting communities nationwide, but certain regions of the country are getting hit harder than others.

In February and March, the Northeast had the highest norovirus positivity rate of any region. The percent of tests coming back positive in Northeastern states, averaged over three weeks, was nearly 10% as of Mar. 30, down from about 16% in late February, per CDC data.

Cities such as Philadelphia have reported spikes in norovirus outbreaks, prompting public health officials to urge residents to take precautions, NBC Philadelphia reported.

"Data from the northeastern region of the United States look similar to what we would expect for this time of year,” a CDC spokesperson tells TODAY.com.

Currently, the hardest-hit region is the Midwest, which saw a three-week positivity rate of over 15% as of Mar. 30, followed by the Western U.S., which had a positivity rate of 12% as of Mar. 30, according to the CDC.

“We’re also seeing a big spike in California,” Dr. Joanna Turner Bisgrove, a family medicine physician and assistant professor at RUSH University Medical Center, tells TODAY.com.

Norovirus cases surged in the Southern U.S. last month as well. An elementary school in Fairhope, Alabama, was closed for two full days in late February due to a suspected outbreak of norovirus that sickened an “alarming” number of students and staff members, NBC News affiliate NBC15 in Mobile, Alabama, reported.

The infamous stomach bug is also spreading at sea. Since January, there have been three confirmed norovirus outbreaks on cruise ships under U.S. jurisdiction, which have sickened hundreds of passengers, per the CDC.

Why is norovirus surging?

Norovirus cases and outbreaks are most common between November and April. “Norovirus is actually a seasonal virus ... and usually the peak within that window is between January and early March," Dr. Ericka Hayes, senior medical director of infection prevention at Children’s Hospital of Philadelphia, tells TODAY.com.

During the colder winter months, people tend to spend more time gathered indoors, which makes it easier for infectious diseases like norovirus to spread quickly between people, says Bisgrove.

The current surge in norovirus is not surprising, the experts note, but rather an expected increase that occurs every winter in the U.S. “It’s following pretty classic trends,” says Bisgrove.

Last winter was a tough norovirus season for the U.S., as virus activity rebounded to pre-pandemic levels following the dropping of COVID-19 restrictions. Cases peaked in early March 2023, but norovirus activity still remained high well into the spring.

In 2023, norovirus outbreaks also surged on cruise ships, reaching the highest levels seen in over a decade.

“Compared to the past years, we are in the same neighborhood, if not a little bit more (in terms of) the number of outbreaks in the region and nationally, but we are well within the normal range,” says Hayes.

How does norovirus spread?

"Norovirus is an extraordinarily contagious virus. It's one of the most contagious kind of pathogens, viral or bacterial," says Hayes.

Infected people shed billions of norovirus particles in their stool and vomit, and it only takes a few virus particles to make another person sick, Hayes adds.

People typically get norovirus when these tiny particles end up in their mouths, TODAY.com previously reported. This can occur through direct person-to-person contact, consuming contaminated food or liquids, or touching contaminated surfaces then putting your unwashed fingers in your mouth.

It can spread rapidly through schools, day cares, nursing homes and other enclosed settings where people are gathered close together, says Bisgrove. Norovirus is also the leading cause of foodborne illness outbreaks in the U.S., per the CDC.

A person who has been infected can continue to shed the virus for about two weeks after their symptoms are gone and they feel better, says Bisgrove.

Norovirus symptoms

These are the most common symptoms of norovirus in children and adults, according to the experts:

  • Vomiting

  • Diarrhea

  • Nausea

  • Stomach cramps

Other possible symptoms include a headache, body aches and a low-grade fever, per the CDC.

The first signs of norovirus may include a sudden loss of appetite, stomach pain or generally feeling out of it, says Bisgrove.

These are typically followed by intense vomiting and watery diarrhea, though these may occur at the same time. "It's usually a very abrupt onset and unfortunately, there's quite a lot of it. ... Patients may have dozens of stools per day," says Hayes.

Norovirus symptoms usually last for 24 to 72 hours. "Due to all the vomiting and diarrhea you may also feel weakness, fatigue or lightheadedness," says Bisgrove.

People with norovirus may become dehydrated due to the loss of fluids through vomit and diarrhea. Symptoms of dehydration include decreased urination, dry mouth or dizziness, per the CDC. Signs in children include crying without tears, becoming fussy or suddenly lethargic and sleepy, says Hayes.

Blood in the vomit or stool is not a normal symptom of norovirus, says Bisgrove, and could be a sign of something more serious. "If you see blood, go to the emergency room," says Bisgrove.

Norovirus treatment

There is no specific treatment or medicine for norovirus, and the vast majority of people will recover on their own at home, the experts note.

It's important to rest and consume plenty of fluids and electrolytes to replenish those lost through vomiting and diarrhea, says Bisgrove. These include water, sports drinks and oral rehydration fluids — but avoid drinks with caffeine or alcohol until you recover.

"We also recommend bland, simple foods (rice, bananas, broths) that (the) body can handle and are more likely to stay down," says Bisgrove.

If symptoms become severe, persist for longer than a few days, or you are unable to keep fluids down or urinate, seek care, says Bisgrove. Some people may need additional support or IV fluids to prevent dehydration or its complications.

Certain groups are at a higher risk of developing complications, including children, the elderly and people with chronic illnesses or weakened immune systems, says Bisgrove.

Children under 5 years old and adults 85 and older are more likely to visit the emergency room, per the CDC.

Preventing norovirus

Norovirus is an incredibly hardy virus. "It's hard to disinfect, and it's resistant to a lot of standard cleaners," says Narula.

Alcohol-based hand sanitizers do not work well against norovirus, the experts note, so good hand-washing is key — this means washing your hands with soap and water for at least 20 seconds, per the CDC. Wash your hands after using the bathroom, after changing diapers and before eating.

If you are sick with norovirus, the experts recommend taking the following steps to prevent spreading the virus to others:

  • Stay home until you feel better

  • Avoid contact with others if possible while sick

  • Wash hands before touching any communal surfaces

  • Clean and disinfect surfaces with bleach

  • Wash laundry in hot water

  • Do not prepare and handle food until at least 48 hours after symptoms stop

This article was originally published on TODAY.com