What Is Gastroenteritis (Stomach Flu)? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Gastroenteritis is often called the “stomach flu,” even though it’s not a type of flu at all. Instead, it’s inflammation of the lining of your intestines.

Most of the time a virus is the culprit, in which case the illness is known as viral gastroenteritis.

Occasionally, bacteria, parasites, or other causes may trigger gastroenteritis. (1)

Avoiding contaminated food and water and making sure to wash your hands frequently may help protect you from this unwelcome condition.

Types of Gastroenteritis

In the United States, viruses are the most common reason for gastroenteritis. (1) Many viruses can cause gastroenteritis, including:

Norovirus This is the most common cause of foodborne illness in the world and affects both children and adults. (2) Most of the time norovirus is passed on through contaminated water or food. It spreads quickly, especially among people in confined spaces. You may have heard about the norovirus affecting passengers on cruise ships. Outbreaks are also common in nursing homes and other places where people are in close contact with one another. Symptoms usually last one to three days. (1,3)

Rotavirus This is the most common cause of viral gastroenteritis in children. (2) It frequently affects babies between 3 and 15 months old. Symptoms last from three to seven days. The virus is usually less severe when it impacts adults. There’s a vaccine available in the United States to protect against rotavirus. Since this vaccine has been introduced, cases of rotavirus have been reduced by about 80 percent. (1,3)

Adenovirus This virus most often affects children under age 2. The symptoms may last 5 to 12 days. (3)

Astrovirus Infants and young children are more likely to get astrovirus, but it can infect anyone. It’s typically spread by the fecal-oral route (where pathogens in fecal particles pass from one person to the mouth of another person, usually through contaminated food or water) and lasts about three to four days. (1)

Gastroenteritis that isn’t caused by a virus may be due to:

Bacteria Salmonella, shigella, campylobacter, Clostridium difficile (C. difficile), and Escherichia coli (E. coli) infections sometimes lead to gastroenteritis. These bacteria can spread by consuming contaminated food or water. (1)

Parasites Most cases of parasitic gastroenteritis are caused by giardia and cryptosporidium. (4) These organisms can be picked up by drinking contaminated water or swimming in a contaminated pool.

Other Causes Ingesting certain drugs or chemical toxins, such as metals or plant substances, can lead to gastroenteritis, although this is rare. (1)

Symptoms of viral gastroenteritis usually start about one to two days after a virus enters your body, and may include: (3)

• Watery diarrhea
• Stomach pain or cramps
• Nausea
• Vomiting
• Muscle aches
• Headache
• Fever
• Chills

Typically, these symptoms last a day or two, but they can persist for up to 10 days. (2,3)

In some people, symptoms of gastroenteritis get worse at night. This happens because your immune system often gets more active at night, and releases infection-fighting substances that cause inflammation and make you feel worse. (5)

Can You Have a Stomach Virus Without Vomiting or Diarrhea?

Gastroenteritis can cause a wide range of symptoms, from mild stomach upset to severe vomiting and diarrhea. Some people even catch, and can spread, the viruses that commonly cause gastroenteritis without showing any symptoms at all. (5)

Gastroenteritis is a contagious illness and is commonly spread by:

• Eating contaminated food (especially raw or undercooked foods)
• Drinking contaminated water
• Being in close contact with an infected person
• Using dirty utensils

Viruses are often passed through the fecal-oral route. This means someone with the virus touches the food you eat without washing their hands after using the bathroom. (2)

Gastroenteritis can affect anyone, but certain people may be at an increased risk, including:

Children and Babies Kids’ immune systems haven’t fully developed, which puts them at risk for catching viruses.

Older Adults As you age, your immune system becomes less effective.

People Who Live in or Visit Group Settings Being in close quarters with others can increase your risk of gastroenteritis. Locations like schools, day cares, nursing homes, cruise ships, and dorms may harbor viruses and bacteria and allow them to spread more easily.

People With a Weakened Immune System Some chronic illnesses, such as human immunodeficiency virus (HIV), can compromise your immune system and make you more susceptible to developing gastroenteritis. (2)

Doctors typically diagnose gastroenteritis by inquiring about your symptoms and performing a physical exam.

Your healthcare provider might ask you questions like:

• When did your symptoms start?
• Have your symptoms been constant, or do they start and stop?
• How severe are your symptoms?
• Does anything you do seem to improve or worsen your symptoms?
• Do you have any signs of dehydration?
• Have you been in contact with other people who have the same symptoms as you?

Your doctor might also order a rapid stool test to see if you have norovirus or rotavirus. Additionally, you might be asked to provide a stool sample to detect a bacterial or parasitic infection. (2)

Sometimes doctors order tests to look for signs of other illnesses that may cause symptoms similar to those of gastroenteritis, including inflammatory bowel disease (IBD). (5)

Gastroenteritis usually comes on suddenly and sticks around for just a short time. The illness typically lasts less than a week.

Most people will get better without any treatments. But you may need certain therapies like intravenous (IV) fluids if you have severe symptoms or become dehydrated. (6)

Gastroenteritis will usually run its course and go away on its own. There’s no specific medical treatment for viral gastroenteritis.

If you have a bacterial or parasitic infection, your doctor might prescribe antibiotics. (1,2)

Physicians usually don’t suggest that you take antidiarrheal treatments like loperamide (Imodium) because they can prolong the infection, especially in children. But these medicines may be beneficial in some cases. (1)

When Should You See a Doctor for Gastroenteritis?

Determining when you should see a doctor for your gastroenteritis depends on your age.

For adults, you should see a doctor if you:

• Have a fever higher than 104
• Can’t keep liquids down for 24 hours
• Have been vomiting blood or have been vomiting for more than two days
• Have bloody bowel movements
• Have signs of dehydration, such as decreased urination, dark-colored urine, dry skin, thirst, or dizziness (2)

For babies and children, you should see a doctor if your child:

• Has a fever of 102 or higher
• Seems to be in pain or discomfort
• Has bloody or severe diarrhea
• Has signs of dehydration, such as dry diapers, lack of tears when crying, dry mouth, drowsiness, or a sunken fontanel
• Has vomiting that lasts more than several hours
• Is unusually irritable, lethargic, or unresponsive (2)

Self-Care for Gastroenteritis

Certain steps can potentially improve symptoms of gastroenteritis and prevent dehydration. You might want to try:

Letting Your Stomach Settle Taking a break from eating solid foods for a few hours at a time may alleviate your stomach troubles.

Avoiding Certain Foods and Substances Stay away from caffeine; alcohol; dairy products; and fatty, sugary, or spicy foods until you start to feel better.

Eating Bland Foods Plain foods are less likely to irritate your digestive system. Crackers, toast, bananas, gelatin, rice, potatoes, and chicken are some good choices.

Staying Hydrated Try to drink plenty of liquids. You might want to suck on ice chips or take small sips of water. Clear sodas, broths, and noncaffeinated sports drinks can keep you hydrated. Children might need an oral rehydration solution, which is available at most pharmacies. (7) If you’re breastfeeding or formula-feeding a baby, continue to feed the child as usual.

Getting Lots of Rest Gastroenteritis can zap your energy. Be sure to rest when you can and get a good night’s sleep. (2)

Prevention of Gastroenteritis

Certain precautions may lower your chances of getting gastroenteritis. These include the following:

Wash your hands often. Proper hygiene, which consists of frequent hand-washing, is one of the best ways to avoid catching a virus. Wash your hands for at least 20 seconds with soap and water after you go to the bathroom and before you eat or prepare food. Be sure to wash around your cuticles, under your fingernails, and in the creases of your hands. Also, teach your kids to wash their hands after using the toilet.

Sanitize. Use an alcohol-based hand sanitizer or wipe if you can’t wash your hands.

Keep areas clean. If someone you’re living with has gastroenteritis, be sure to disinfect all surfaces with a bleach-based cleanser. Try using a ratio of between 5 tablespoons and 1.5 cups of bleach to 1 gallon of water.

Avoid contaminated foods or water. Don’t eat or drink any foods that may make you sick, such as raw or undercooked meats. Consume only pasteurized dairy products and apple juice. Rinse all produce well before preparing or eating it.

Don’t share personal items. Avoid drinking from the same glass, can, or bottle as others, and don’t share utensils or towels.

Stay away from others. If people you know are sick, try to keep your distance. If you’re sick, stay away from people, and don’t prepare food for anyone while you’re sick or for two days afterward.

Vaccinate children. A vaccine is available in some countries, such as the United States, to protect babies from rotavirus. It’s typically administered during a baby’s first year of life.

Examine your child’s day care facility. Make sure the center has separate diaper-changing and eating areas. There should also be a sink near the changing table to wash hands. (2,5)

Tips to Prevent Gastroenteritis While Traveling

Many people develop gastroenteritis when they visit other countries. This usually happens because they drink unclean water or eat contaminated foods. This is commonly called traveler’s diarrhea.

When you’re traveling, use sealed, bottled water to drink and brush your teeth. Avoid ice cubes, as they can contain contaminated water. You can also take 2 tablets of Pepto-Bismol 4 times a day before you travel and while you are traveling to help prevent diarrhea. Do not take Pepto-Bismol for more than 3 weeks.

Be sure to wash or sanitize your hands often while you’re out and about.

Also, play it safe when it comes to the foods you eat. It’s a good idea to avoid raw foods, such as veggies, peeled fruits, and salads. Steer clear of undercooked meat and fish, too. (2)

If you have gastroenteritis, dehydration is the main complication to worry about. This happens when you lose an extreme amount of water, salts, and minerals.

Signs of dehydration may include: (8)

• Extreme thirst
• Urinating less often
• Dark-colored urine
• Dizziness
• Fainting
• Tiredness
• Lack of energy
• Sunken eyes

If babies become dehydrated, they might:

• Cry without tears
• Have a dry mouth and tongue
• Have no wet diapers for three hours or longer
• Be very sleepy or drowsy
• Have a fever
• Be especially irritable

Severe dehydration can lead to organ damage, shock, a coma, or even death. (6)

Sometimes serious cases of dehydration may require a hospital stay, so you can receive IV fluids. Infants, older adults, and people with compromised immune systems are at a greater risk of developing severe dehydration. (2)

Norovirus is estimated to cause between 19 and 21 million cases of viral gastroenteritis each year in the United States. (6) Data on other, less common types of gastroenteritis isn’t readily available.

Worldwide, severe gastroenteritis is believed to cause over one million deaths each year. About one-half of these deaths occur in children. (1)

Certain diseases may cause symptoms similar to those of gastroenteritis, including inflammatory bowel disease (IBD). But the onset and duration of symptoms is likely to be different for IBD. (5,9)

Although gastroenteritis is sometimes referred to as the “stomach flu,” it’s not a form of influenza. The flu viruses do not cause gastroenteritis, and a flu vaccine won’t protect against it.

Flu viruses are responsible for respiratory infections that affect your nose and throat, and sometimes your lungs. Gastroenteritis affects your intestines. (1,6)

Dealing with gastroenteritis can be scary and difficult, and you may want to look for other sources of information and support. The following resources may help:

• Foodborne Germs and Illnesses, Centers for Disease Control and Prevention (CDC)
• Norovirus, CDC
• Food Safety Charts, FoodSafety.gov
• Stomach flu: How Long Am I Contagious? Mayo Clinic

Questions to Ask Your Doctor About Gastroenteritis

You might want to bring a list of questions to your or your child’s appointment. Some questions to ask your doctor include: (2)

• What’s causing my symptoms?
• Do I need any tests to confirm my diagnosis?
• What types of measures should I take to avoid spreading this illness?
• What treatments are available? Are there other or complementary approaches?
• How long will my symptoms last?
• What can I do at home to improve my symptoms?

Gastrointestinal sometimes symptoms occur in many people who develop COVID-19, although they don’t affect everyone with the viral infection. These symptoms may include nausea, vomiting, and diarrhea, and they may develop before the onset of fever or respiratory symptoms. (10) If you develop gastrointestinal symptoms followed by respiratory symptoms, contact your doctor to discuss whether you need to be tested for COVID-19. (11)