CDC Data Show Stomach Flu is Rising Across US: Know these symptoms

It’s officially stomach flu season in the United States. If you’ve ever experienced a gut-wrenching bout of gastrointestinal illness, you know how miserable it can be.

What we know as the “stomach flu” or “stomach bug” is typically a case of norovirus, a highly contagious virus that causes vomiting and diarrhea. Despite its nickname, norovirus is not related to influenza.

Right now, outbreaks of norovirus are on the rise in the 14 states that report data to the CDC’s NoroSTAT program, Kate Grusich, CDC spokesperson, tells TODAY.com in a statement. In the period between Aug. 1, 2022 and Jan. 8, 2023, there were 225 norovirus outbreaks reported to the CDC, compared to 172 outbreaks during the same period the previous season, per the CDC.

“While norovirus cases are rising in the U.S., CDC data as recent as January 2023 show that reported norovirus outbreaks are within the expected range for this time of year,” says Grusich.

However, some experts tell TODAY.com they’re bracing for a winter surge in norovirus, especially among children.

Here’s what to expect this norovirus season and what experts want you to know about symptoms, transmission, treatment and prevention.

Will there be a norovirus surge this year?

Each year in the U.S., norovirus causes 19 to 21 million cases of vomiting and diarrhea, 109,000 hospitalizations and 900 deaths, according to the U.S. Centers for Disease Control and Prevention.

Although it can spread year-round, norovirus is a seasonal illness that typically spikes during the winter and early spring, Grusich says. Most outbreaks occur between November and April, according to the CDC.

It’s too early to tell if there will be a norovirus surge in the U.S. this year, but it is clear that cases are rising.

“It’s going up quickly right now. It’s not yet at the peak we’ve seen in previous years, but it’s definitely on the rise and pretty suddenly in the past few weeks,” Dr. Ali Alhassani, a pediatrician at Boston Children’s Hospital, tells TODAY.com.

A surge in norovirus outbreaks could lead to an increased number of hospital visits, Alhassani notes, or a reduction in the already-strained health workforce.

“We’ve always had seasonal increases and waves of norovirus, and our hospitals would be filled with kids,” Dr. Albert Ko, infectious disease physician and professor of public health, epidemiology and medicine at Yale School of Public Health, tells TODAY.com. “What kind of took us off was the pandemic.”

“I would be surprised if this year’s peak is worse than last year’s. … I think we’re going to be starting to get back to the epidemiological pattern that we normally see,” says Ko.

Dr. Luis Ostrosky, an infectious disease specialist at UTHealth Houston and Memorial Hermann in Houston, tells TODAY.com that “norovirus activity is higher and earlier than usual (right now), but definitely not a big outlier compared to pre-pandemic levels.”

The total number of outbreaks reported during the 2022-2023 norovirus season is within the range reported during the same period during past norovirus seasons from 2012–2020, says Grusich.

How does norovirus spread?

Norovirus is transmitted primarily “when bacteria or viruses shed in stool ends up on our hands and surfaces and then eventually ends up in our mouth and we ingest it and get infected,” says Alhassani.

Norovirus may be transmitted directly from an infected person or from contaminated surfaces, objects, foods or drinks.

“Anybody who is in close contact with someone who has an active infection with norovirus is at high risk of getting it,” says Alhassani. Norovirus can spread through activities like caring for an infected person, changing diapers or sharing utensils.

“Norovirus is so infectious that even if somebody throws up and there’s droplets of vomit aerosolized in the air, that can actually cause infection,” Alhassani adds.

It takes a very small number of virus particles to transmit the disease, says Ko, which is why norovirus causes so many explosive outbreaks. Per the CDC, less than 100 norovirus particles can make you sick, and infected people typically shed billions of particles.

Outbreaks often occur in schools, day cares, nursing homes and cruise ships, the experts note.

What are the symptoms of norovirus?

The most common symptoms of norovirus are vomiting, nausea, diarrhea and abdominal pain, says Ko. Other possible symptoms include a headache, body aches and a low-grade fever. Norovirus symptoms usually develop within 12 to 48 hours after exposure, per the CDC.

“Norovirus … will just last a few days,” says Ostrosky. “For the majority of the population, it’s going to be just a nuisance.”

Those at higher risk of developing severe or prolonged symptoms include babies, the elderly and the immunocompromised, says Ostrosky. If symptoms transition into chronic diarrhea and weight loss, this can lead to complications like dehydration or poor absorption of medications, he adds.

What is the treatment for norovirus?

“There’s actually no specific treatment or antiviral for norovirus,” says Ostrosky. Hydration is key to replenish fluids lost from vomiting and diarrhea, the experts note, which means drinking plenty of water, Pedialyte or sports drinks.

“Then it’s just eating bland foods and trying to let it pass through the body, which usually takes like one to three days,” says Alhassani, adding that over-the-counter anti-nausea medicine and pain relievers may also be used to ease symptoms.

“The vast majority of people can be managed at home and, in fact, should be isolated at home until they’re improving, given how contagious norovirus can be,” says Ostrosky.

However, it’s important to watch for signs of severe dehydration and to contact a health care provider if these occur, the experts note. These include dry mouth, decreased urination, dizziness and, in children specifically, crying without tears, fussiness or unusual sleepiness, per the CDC.

Children under 1, people who are immunocompromised, or those with prolonged or severe symptoms should also be seen by a physician, says Alhassani. “While it infects many people, (norovirus) tends to not send as many people into the hospital and certainly the ICU,” he adds.

After recovering from norovirus, you may possibly develop some immunity, says Ko, but it won’t be robust, and it wanes over time, so you can be reinfected with norovirus multiple times.

“It’s only partial immunity … because there are different types of norovirus, and being exposed to one doesn’t give you complete protection to another,” he says.

How can you prevent norovirus infection?

There’s no vaccine against norovirus, says Ko, but there are steps you can take to prevent infection and transmission.

Hand hygiene is extremely important — but the way you clean your hands matters, Ostrosky notes. Hand sanitizer won’t cut it.

“Norovirus is one of the few viruses that doesn’t get deactivated by alcohol. You actually need to use soap and water to physically destroy it and remove it from your hands,” says Ostrosky.

Wash your hands after using the restroom, before eating or cooking and after caring for someone with norovirus.

When cleaning surfaces or objects that may be contaminated with norovirus, Ostrosky suggests using a high-level disinfectant like bleach.

If you or your child are sick with norovirus, isolate to prevent the virus from spreading within the household, says Alhassani. Anyone sick with norovirus should stay home until they feel better.

“We can expect to continue seeing more viral illnesses, both respiratory and gastrointestinal, in this post-COVID era we’re sort of approaching,” says Ostrosky, adding that the basics of hand-washing, isolation and respiratory etiquette can go a long way.