Is It Norovirus, a 'Stomach Bug' or Something Else?

Yahoo

06-02-2025

Norovirus outbreaks are popping up around the United States, causing concern during a winter when other illnesses also seem especially virulent. "Between August 1, 2024, and January 15, 2025, the Centers for Disease Control and Prevention tracked 1,078 norovirus outbreaks among participating states through its NoroSTAT monitoring system -- a significant jump from the 557 outbreaks reported during the same period last seasonal year. This increase is also higher than outbreak levels seen in previous seasonal years (2012–2020 and 2021–2024)," says Dr. Patricia Pinto-Garcia, MD, MPH and medical editor at GoodRx.
With an estimated 19-21 million norovirus illnesses a year in the United States, norovirus is both a common illness and commonly confused with other illnesses. We talked to doctors who see norovirus in the broader landscape of infectious diseases, giving us the details on what distinguishes norovirus and how we can treat it, heal and prevent its continued spread.
Norovirus is a rapid-onset viral infection that manifests with gastrointestinal symptoms. Norovirus is spread by contact with the virus on surfaces, in food or by touching a person who has the virus. It doesn't take much virus to infect someone new, making it highly contagious. Plus, you aren't necessarily immune even if you've had norovirus before in recent weeks or months, since it can come from different strains of the virus.
Pinto-Garcia says norovirus symptoms can persist longer in young children, older adults and anyone with a weakened immune system. Although it is most common during the fall and winter, it also occurs year-round.
Norovirus is not always diagnosed through testing since only around 13% of cases prompt a doctor's or hospital visit. The symptoms are distinctive, and treatment is often similar whether gastrointestinal symptoms are specifically due to norovirus or not.
"The classic symptoms are nausea/vomiting, abdominal pain/cramping and watery diarrhea. Vomiting is more common with norovirus than many other viruses," says Dr. Kari Neemann, MD, pediatric infectious disease specialist at Children's Nebraska in Omaha. "Other possible symptoms include fevers, body aches and headache. Once you become infected you generally will develop symptoms in 12-48 hours (rapid onset). Duration of symptoms is most commonly 1-3 days."
While norovirus symptoms tend to abate within three days, the impact of dehydration and other secondary symptoms, like lack of appetite, may take longer to resolve. Those who have experienced norovirus will still be contagious for weeks after their symptoms are gone, so it is particularly important to continue a rigorous hand-washing regimen and sanitize surfaces during the weeks after infection.
The stomach flu or "stomach bug" doesn't usually refer to an influenza virus; even when the flu has gastrointestinal symptoms, it is primarily a respiratory illness that may also produce fever, aches and fatigue. Stomach flu and "stomach bugs" are a conversational way to refer to any illness that produces gastrointestinal symptoms like diarrhea or vomiting.
People may refer to their symptoms as the stomach flu. Still, it is wise to treat anyone with severe gastrointestinal symptoms as if they could have norovirus, prompting those around them to sanitize surfaces and wash hands regularly. Treatment of severe gastrointestinal symptoms, even when not identified as a particular "stomach bug" like norovirus, is typically focused on rest and hydration.
Rotavirus is an illness more common in infants and young children that presents some symptoms similar to norovirus, but knowing its course can help you avoid worrying if a child has symptoms that are out of the ordinary for norovirus.
"[Rotavirus] infection usually begins with acute onset of vomiting, followed 24-48 hours later by watery diarrhea and can be associated with fevers," says Neemann. "Here, symptoms develop a bit slower than norovirus. Onset of symptoms is usually from 1-3 days of exposure, and symptoms last longer than norovirus at 3-7 days."
Rotavirus vaccines are available and scheduled when infants are only a few months old to prevent severe illness. While the standard progression of rotavirus takes longer than norovirus, in both illnesses, the most important signs to watch for are signs of severe dehydration.
"Children who are dehydrated will often have decreased urine output (less than one wet diaper or void in six hours), may cry with few or no tears, have dry mouth, sunken eyes, cool or clammy hands and feet and may become more sleepy or fussy," says Neemann. "These would all be indications to seek immediate medical attention."
Your doctor might also weigh in on whether they suspect rotavirus or norovirus is to blame, but they may also focus on treating the dehydration.
Food poisoning is an umbrella term for any virus or bacterial infection that produces severe gastrointestinal symptoms and is acquired through inadequate safety measures when preparing food. Norovirus can be transmitted this way and is estimated to cause 58% of foodborne illnesses in the United States, but other infectious agents can also be transmitted in food.
Food poisoning should be treated the same way you'd treat norovirus at home, in the sense of working hard to stay hydrated and rest until symptoms ease.
While COVID can be accompanied by gastrointestinal symptoms, it is primarily a respiratory infection and will typically present differently from norovirus. Similarly, influenza A and B can present with a variety of symptoms but typically include some respiratory symptoms.
If you have co-occurring severe gastrointestinal symptoms with respiratory symptoms or sore throat, you can check using an at-home test to see if either the flu or COVID is present. Since it is also possible to have co-infections with more than one illness present, it's wise to watch for dehydration and treat yourself with rest, hydration and a bland, easy-to-digest diet.
Typically, norovirus treatment is managed at home. The most important treatments are resting when possible and rehydrating with water or oral rehydration fluids like Pedialyte, which should be consumed in very small amounts until vomiting stops.
"Drinking electrolyte-rich fluids, like sports drinks or hydration supplements, can help replace lost fluids," says Pinto-Garcia. "There's no antiviral medication for norovirus, but if nausea is severe, your doctor may recommend Zofran (ondansetron) to help. When it comes to diarrhea, check with your provider before taking anti-diarrheal medications -- sometimes, it's better to let your body clear the virus naturally. They may also suggest probiotics or probiotic-rich foods, such as yogurt, kefir or kimchi, to help your gut recover faster."
The main risk factor in these illnesses is becoming too dehydrated, but persistent symptoms may indicate a different problem if norovirus weakens your immune system.
"In some cases, another illness -- like a bacterial infection that requires antibiotics -- could be to blame. You should also seek medical attention if you notice signs of severe dehydration, including fast heartbeat, rapid breathing, dizziness, extreme fatigue, confusion or trouble thinking clearly," says Pinto-Garcia. "If something feels off or symptoms aren't improving, it's always best to check in with a healthcare professional."
Norovirus outbreaks are fought with good hygiene and information. In any setting where a lot of people are in contact with each other, like schools, daycare centers, long-term care facilities and hospitals, it's essential that people wash their hands with soap and water since hand sanitizer is less effective against norovirus. Frequently cleaning surfaces with a bleach solution is also helpful; just remember that bleach products shouldn't be used in combination with other cleaning products, since they can react and produce harmful compounds.
Information is the other crucial piece of the puzzle. If someone was in physical proximity to others right before they experienced sudden and severe symptoms that could be norovirus, they should let people know. That way, everyone can redouble their hand-washing and sanitizing efforts. Schools can implement extra cleaning and avoid contact with children with symptoms so that any outbreaks are as contained as possible.
It does seem like a tenacious strain of norovirus is moving through the United States this winter, as Pinto-Garcia points out: "The CaliciNet data from the CDC shows that more than 70% of norovirus cases in fall 2024 were caused by a strain called GII.17. It's possible this strain causes more serious illness or spreads more quickly, which could account for why we saw such a high jump." It's wise to exercise extra caution until outbreak numbers drop.
Even during a norovirus outbreak, preventing norovirus and managing norovirus symptoms follow the same protocol. Rigorous hand-washing with soap and treating surfaces regularly with CDC-recommended, bleach-based cleaning solution help keep infection at bay. If norovirus does enter your home or school, treating active norovirus symptoms with rest and hydration will offer you the best path through the symptoms and back to health.