How long does a stomach bug last?

A stomach bug is fast-acting, but it’s easy to confuse it with other illnesses. Here’s what to expect.

By Heidi Borst | Sep. 25, 2023 Medically reviewed by Jesse P. Houghton, MD, FACG

It’s an unfortunate scenario most of us are familiar with: You wake up in the middle of the night in the grips of an unwanted visitor: stomach flu. Your body is in full-on rebellion, and you have no control over the relentless symptoms, from vomiting to diarrhea. After a day or two of suffering, you just want to know when it will end.

Most stomach bugs typically last only a few days but can linger for two to three weeks in severe cases. Here’s what you need to know about stomach virus causes, symptoms, and remedies.

How long does a stomach virus last?

The duration of stomach flu depends on many factors, says Jared Braunstein, DO, a board-certified internist at Medical Offices of Manhattan, such as which virus is causing the sickness, the patient’s general health, and how well they manage their symptoms.

Here’s a general timeline based on virus type:

Norovirus: Symptoms start within 12 to 48 hours of exposure, typically lasting one to three days.
Rotavirus: Symptoms begin about two days after exposure, typically lasting three to eight days.
Adenovirus: Symptoms start three to 10 days after exposure, typically lasting five to seven days, but can last up to two weeks.
Astrovirus: Symptoms begin four to five days after exposure, typically lasting one to four days.
Sapovirus: Symptoms start 12 to 48 hours after exposure, typically lasting two to six days.

“It’s important to keep in mind that these are just rough figures and that each person’s experience may be different,” says Dr. Braunstein.

What causes stomach flu?

The stomach flu, or gastroenteritis, is inflammation of the stomach and intestinal lining, says Hannah Newman, MPH, senior director of infection prevention at Northwell Health Lenox Hill Hospital in New York. Causes of stomach flu include:

Viruses
Bacteria
Parasites
Chemicals
Reactions to medications
Reactions to food

Here’s where it gets a bit confusing: Food poisoning is technically a type of gastroenteritis resulting from consuming foods or beverages contaminated with viruses, bacteria, parasites, or chemicals. In contrast, the term “stomach flu,” although not medically accurate, typically refers specifically to gastroenteritis caused by viral infections — the most common cause of the disease. The most common culprits of viral gastroenteritis are:

Norovirus
Rotavirus
Astrovirus
Adenovirus
Sapovirus

The names are similar, but stomach flu is not the same disease as influenza, typically referred to as simply “the flu.” General flu and stomach flu are caused by different types of viruses affecting different parts of the body—the respiratory system for the former and the digestive system for the latter—says Dr. Braunstein.

Stomach flu symptoms

Viral gastroenteritis comes on suddenly, usually lasts for less than one week, and most people get better on their own without medical treatment. According to Dr. Braunstein, stomach flu viruses affect the digestive system, causing symptoms like:

Nausea
Vomiting
Diarrhea
Stomach cramps
Loss of appetite
Fever
Fatigue
Dehydration (in cases of severe illness)

“While these symptoms are typical for most stomach flu viruses, there are differences in terms of which age groups are more affected and the severity of the illness,” Dr. Braunstein says. For instance:

Norovirus infections often cause acute and rapid gastrointestinal distress, says Dr. Braunstein, adding that people of all ages are vulnerable to it. He says that because norovirus is highly infectious, it poses a significant threat of outbreaks to institutional settings, including hospitals, schools, and cruise ships.
Rotavirus primarily affects toddlers and newborns and is largely preventable with one of the rotavirus vaccinations, Rotarix or Rotateq. Young children who contract rotavirus are at risk of severe dehydration due to the combination of vomiting and watery diarrhea, Dr. Braunstein says.
Adenovirus is actually a group of viruses that can cause many illnesses, including the common cold. Some strains cause gastroenteritis, and children under 5 are particularly susceptible.
Sapovirus and astrovirus are less prevalent than other stomach flu viruses but induce comparable symptoms, says Dr. Braunstein. While all age groups are susceptible, astrovirus is most common in children, adults over 65, and those with weakened immune systems; sapovirus is most common in children under 5.

“Sometimes it’s hard to tell the difference between stomach flu (viral gastroenteritis) and other [gastrointestinal] GI diseases since the symptoms are similar,” says Dr. Braunstein. Although both influenza and stomach flu may cause fever and fatigue, for example, the former leads to more respiratory symptoms such as a cough, sore throat, runny nose, congestion, chills, body aches, and headaches.

And while gastrointestinal issues do sometimes occur with influenza, they happen less often (and are generally not as bad) as those that accompany the stomach flu, says Dr. Braunstein.

Still unsure what you have? Dr. Braunstein shares these tips to help you differentiate between viral gastroenteritis and other illnesses:

Sudden onset: The stomach flu is frequently unexpected. One minute you could feel good; the next, you might be sick with nausea, vomiting, and diarrhea.
Fever: The stomach flu may cause a slight fever, but a high temperature with respiratory symptoms might indicate another illness, such as influenza.
Duration: Most people recover from the stomach flu within a week, and usually after two to three days. The longer symptoms like stomach pain, vomiting, and diarrhea last, the more likely something else is the cause. “The abrupt onset of the stomach flu is unlike the persistent symptoms of irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and food intolerances,” says Dr. Braunstein.

If you want more certainty, see a healthcare provider. They can determine if the cause of your symptoms is stomach flu or another gastrointestinal illness, Newman says, adding that stool tests can help with diagnosis.

During your illness, it’s essential to stay refreshed by drinking water, especially if you’re throwing up or having diarrhea, advises Dr. Braunstein. And if your symptoms are severe, last longer than the typical timeline, or come with worrying signs like a high fever, blood in your stool, or signs of dehydration, he urges you to see a healthcare provider.

Stomach flu remedies

Even though there is no special treatment for viral gastroenteritis, you can do a few things to ease the symptoms, says Dr. Braunstein. To get better as quickly as possible, try these suggestions:

Sip clear liquids like water, broth, and oral rehydration solutions like Pedialyte or sports drinks containing electrolytes.
Get extra sleep to give your body time to recover and fight off the virus, advises Dr. Braunstein.
Follow the BRAT diet by eating bland solid foods like bananas, rice, applesauce, and toast for a day or two while your stomach recovers. Avoid dairy products, fatty or spicy foods, caffeine, and alcohol, all of which can aggravate the stomach. Healthcare providers do not recommend this diet for everyone, so be sure to check with yours first.
Consume ginger ale, ginger tea, or ginger candies, which may help soothe nausea and ease stomach discomfort, Dr. Braunstein says.
Consider probiotics supplements, which may help shorten the duration and decrease the severity of your symptoms. However, it’s best to consult with your healthcare provider before taking these products.
Try over-the-counter (OTC) medications like Imodium A-D (loperamide) and Pepto-Bismol (bismuth subsalicylate), which can help relieve diarrhea in adults. Children should avoid Pepto-Bismol during a viral illness as a rare syndrome called Reye’s syndrome can occur.
Talk to your healthcare provider about prescription medications like Zofran (ondansetron), which helps control severe vomiting.

Is the stomach flu contagious?

Gastroenteritis caused by viruses, bacteria, or parasites is contagious from person to person. If you touch your nose, eyes, or mouth after contact with a germ-covered surface, you may become infected with the stomach flu.

“Most people get the stomach flu when they eat, drink, or touch something infectious,” says Dr. Braunstein. It also spreads through direct contact with an infected person or by sharing food, drinks, or eating utensils.

Gastroenteritis does not, however, travel through the air like the general flu (influenza) or the common cold. The latter two spread through droplets in the air when a sick person coughs, sneezes, or talks, Dr. Braunstein explains.

There are some things you can do to minimize your chances of contracting stomach flu, though. These include:

Wash your hands frequently with soap and water, especially before eating and using the restroom and changing diapers (hand sanitizer will work in a pinch, but is less effective).
Wash fresh fruit and vegetables before eating.
Cook meats and shellfish to the recommended temperatures.
Disinfect common surfaces with a bleach solution if someone in your home is ill.
Avoid contact with sick people or stay home if you are sick.

“It’s best to self-isolate until two days after your symptoms have stopped (when you’re most contagious) to prevent transmission to others,” Newman says.

When to call your healthcare provider

Contact a healthcare provider if any of the following signs are present:

You can’t keep liquids down for 24 hours or more.
There’s blood or pus in your vomit or stool, or your bowel movements are black or tarry.
You’re showing signs of dehydration like dark urine, weakness, headache, thirst, and dry mouth. Pediatric patients may experience decreased urination (less than four wet diapers in 24 hours), dry eyes and mouth, no tears, sleepiness, irritability, grayish skin, sunken eyes, or a sunken soft spot (fontanel) on the front of the head.
You have severe abdominal pain.
You have a fever over 102 degrees Fahrenheit.
You are experiencing mood changes, such as irritability or lack of energy.

Healthcare providers can treat dehydration with IV fluids and sometimes prescribe medication to reduce vomiting or diarrhea in adults, says Newman.

The bottom line? Some people may feel better in a day or two, while it may take longer for others, says Dr. Braunstein. If you’re sick, it’s important to stay hydrated and give your body time to rest, but if you have severe or long-lasting symptoms, seek medical attention from a primary care provider or pediatrician.