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Flu vs. the Stomach Flu

How to tell which “flu” you have—and how to prevent them both.

Is the stomach flu the same as the flu?

Even though the “flu” and the “stomach flu” both make us feel awful, they are two entirely separate diseases—and it’s important to know how to tell the difference between them.

Gastroenteritis is the medical term for what is commonly called the “stomach flu.” It is not the same as influenza, which we know as “the flu.” The two illnesses can sometimes have similar symptoms, but they are caused by different germs.

Causes of the flu and stomach flu

Flu

The flu is caused by an influenza virus that targets the respiratory tract—your lungs, your windpipe (trachea), your nose, and the back of your throat. There are different types of flu viruses, with influenza Type A and Type B causing most cases of influenza.

Stomach flu

Like influenza, the stomach flu can be caused by viruses, namely rotavirus or norovirus. But while influenza is only caused by viruses, stomach flu can also be caused by bacteria like E. coli or Salmonella in contaminated food, or even by a parasite like Giardia, which you can pick up from activities like swimming in freshwater lakes or drinking from them. Less commonly, stomach flu can also be triggered by toxins or chemicals.

Most common symptoms

Pro Tip

While both the stomach flu and food poisoning generally have similar symptoms and treatments (e.g. hydration), they are different. Food poisoning is a type of gastroenteritis like the stomach flu, but it generally happens very quickly—within hours—after ingesting contaminated food. Stomach flu, commonly caused by viruses, usually develops gradually over a few days. —Dr. Petrina Craine

Flu symptoms

Because the flu targets the respiratory tract, its most common symptoms are cough, sneezing, congestion, runny nose, sore throat, and chest discomfort. But you may also feel full-body symptoms like fever (especially a high fever), chills, fatigue, weakness, body and muscle aches, and headaches.

Many people with the flu can also experience gastrointestinal symptoms, such as diarrhea, vomiting, and nausea. When they happen with the flu, it is more often in children than in adults.

Stomach flu symptoms

The most common symptoms of gastroenteritis are nausea, vomiting, belly cramping and pain, and diarrhea (which can be frequent). Children and infants are more likely to have poor feeding and decreased appetite with the stomach flu. Some people may also have a fever. A key difference between stomach flu and the flu is that the stomach flu does not cause respiratory symptoms like the flu does.

How is the stomach flu spread?

The stomach flu is very contagious, and it can spread in different ways. You can catch it from coming in contact with someone who has it (particularly contact with their stool and vomit). Or by eating, drinking, or touching things that an infected person has contaminated.

Using the bathroom or handling human waste (like after changing a baby’s diaper) and then not washing your hands before preparing food is one way to spread the disease. Sometimes, it can be caused by bacteria in foods like raw or undercooked meats, or by prepared foods that have been contaminated by germs.

You will usually begin to have symptoms 1 to 2 days after being infected. Especially if it’s caused by a virus, the stomach flu can be very contagious and often can affect large groups of people who are in close contact, such as an entire household, a daycare or school, a prison, a dormitory, nursing home, or a cruise ship.

How is the flu spread?

The flu spreads through respiratory droplets from coughing, sneezing, or talking. You can catch it from inhaling air that has droplets of the virus, even if you’re not very close to a person who has it. You can also get it by coming in contact with droplets when they land on your hands or on shared objects like tables, doorknobs, or utensils.

You will typically start to have symptoms 2 days after being infected, but symptoms can take as long as 1 to 4 days to show up. You are most contagious during the first 3 to 4 days of showing symptoms. The flu is contagious and can often spread like wildfire in large groups of people in close contact, such as dormitories, military barracks, schools, and nursing homes.

How long do the flu and stomach flu last?

Flu

In many people with the flu, symptoms go away in about 5 to 7 days. In some more vulnerable groups, symptoms may last longer and they are more likely to have complications. These groups include those with weakened immune systems, people with chronic health problems such as diabetes and high blood pressure, pregnant women, children, and older adults.

Stomach flu

For most people who are otherwise healthy, the stomach flu typically lasts for 1 to 10 days.

Some groups, such as the elderly, children and infants, and people with compromised immune systems, may experience symptoms that last longer and are more severe.

Treatments for the flu

Pro Tip

Good health habits, such as eating healthy food, exercising, getting enough sleep, and practicing good hygiene (e.g. washing your hands regularly) are your best first defenses toward preventing and fighting off various germs. They can help cause a domino effect of protection for your body! —Dr. Craine

Although having the flu can make you feel terrible, most people with the flu will get better at home on their own. Be sure to stay hydrated and get enough rest.

Medications

  • Take over-the-counter medications for fever and body aches: acetaminophen (Tylenol) and ibuprofen (Advil).
  • There are antiviral medications (such as Tamiflu) that can be used to treat the flu. These are recommended for people with or without chronic health problems and who are diagnosed with the flu and have had symptoms for up to 48 hours. They also are recommended, even after the 48-hour period, for people considered at high risk for developing complications from the flu (e.g., pregnant women and people with chronic lung problems like asthma) or those who are hospitalized.

Treatments for the stomach flu

As with the flu, many people with the stomach flu recover on their own. It is very important to stay hydrated, as the body can lose a lot of water and electrolytes (essential minerals) during this time from throwing up, diarrhea, and fever. If you have the stomach flu:

  • Drink plenty of fluids (e.g. water or rehydration drinks that replenish electrolytes) to stay hydrated. Infants can try bottle feeding with regular formula or rehydration drinks placed in bottles, usually taking in smaller amounts with more periods of rest in between sips. If an infant is breastfed, it’s ok to try to continue to breastfeed.
  • Don’t worry if you don't feel like eating much. If you do eat, have foods that are gentler for your digestion, like bananas, crackers, rice, and toast.
  • Avoid eating foods that can increase irritation in your digestive tract like spicy foods, very sugary foods, alcohol, caffeine, milk, or fatty foods.

Medications

  • Because many stomach flus are caused by viruses, antibiotics—medicines that treat bacterial infections—won’t help, and can in fact make things worse.
  • If you have a stomach flu caused by bacteria or a parasite, your doctor may prescribe antibiotics or antiparasitic medications.
  • Medications to stop diarrhea aren’t usually recommended, since diarrhea is one way to rid the infection from your system. But your doctor may decide to give them to you on a case-by-case basis.

When to see a doctor for stomach flu

Some people can develop severe symptoms or complications from gastroenteritis. Get medical help immediately if you have the stomach flu with:

  • Vomit or stool with blood or mucus in it.
  • Signs of severe dehydration: being unable to urinate, making very little or dark urine (or fewer wet diapers in babies), sunken skin or eyes, not being able to make tears, very dry mouth, extreme thirst, or skin that doesn’t go back when gently pinched.
  • Dizziness, confusion, fainting, excessive sleepiness, or fussiness (especially in infants or children).
  • Constant belly pain or swelling.
  • Vomiting to the point where you can’t keep any liquids or food inside your digestive tract.
  • Fever, especially fever for more than 5 days or fever in infants (greater than 100.4°F) or greater than 102.2°F in an older child or adult.

When to get help for the flu

Most people recover from the flu, but it is important to remember it can be a deadly infection. Since 2010, an estimated 12,000 to 61,000 people per year in the U.S. have died from influenza and its complications, such as pneumonia, infections of the heart or brain, severe muscle damage (rhabdomyolysis), and organ failure, according to the Centers for Disease Prevention and Control. Get medical attention immediately if you have the flu with:

  • Difficulty breathing.
  • Chest discomfort.
  • Blue lips, face, or skin.
  • Signs of severe dehydration (being unable to urinate, making very little or dark urine (or fewer wet diapers in babies), very dry mouth, extreme thirst, etc).
  • Dizziness, confusion, fainting, excessive sleepiness, or fussiness (especially in infants or children).
  • Fever, especially fever for more than 5 days or fever in infants (greater than 100.4°F) or greater than 102.2°F in an older child or adult.
  • Severe weakness or muscle or body aches, especially if they prevent walking or crawling.
  • Seizures.
  • Symptoms like fever or cough that get better, but then come back and get worse.
  • Chronic medical conditions (like asthma) that get worse.

How to prevent getting either flu

Dr. Rx

Once a patient told me he was vaccinated twice for the flu in the same season for “extra protection.” No studies to date have shown that it helps to get more than one dose of the vaccine during the same flu season. Unless recommended by your doctor (such as for a child getting a flu shot for the first time), save yourself from the extra needle jab—only one dose is recommended for each season. —Dr. Craine

Although the flu and the stomach flu are very different diseases, the steps you can take to keep from getting them do overlap. Protect yourself by doing the following:

  • Get a flu vaccine every year, in the fall. This is one of the most important steps nearly everyone can take to protect against influenza. (While there are vaccines available for some types of stomach flu like those caused by rotavirus, healthy adults usually don’t need those shots.)
  • Wash your hands with soap and water for about 15 to 20 seconds, and do it often. You can also use alcohol-based hand sanitizer when you aren’t able to wash your hands.
  • If you have the stomach flu, try to use a toilet set aside for you, to decrease the risk of others having contact with your infected body fluids. If that’s not possible, sanitize and clean toilet areas frequently with disinfecting products. If you have the flu, remember that it can be spread by respiratory droplets that land on shared objects, so sanitize areas like doorknobs, faucets, phones, TV remotes, and light switches that people touch often.
  • Avoid handshaking.
  • To keep from getting or spreading the flu, wear a mask to help protect yourself and others.
  • Do not go to work if you have the flu or the stomach flu. Work from home if you can, as you recover.
  • Do not help cook or prepare food or drink for others while you are sick.
  • Store, cook, and serve food safely. Keep perishable food in the refrigerator. Cook meats to the right temperature and clean sinks, countertops, dishes, and your hands after handling raw meat or fish. Be sure foods that can spoil (especially those with milk, cream, eggs, or mayonnaise) don’t stay out for too long, especially in warm temperatures.
  • Practice social distancing and limit contact with people who have the flu or stomach flu.
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