Is it Cold, Flu or Something Else?

Watch out for these telltale signs to recuperate faster—and avoid possible complications.

Medically reviewed in August 2020

You feel like crud. Achy, tired, runny nose, congestion—maybe an upset stomach. But you know what to do: drink fluids, stay home and rest up till you feel better.

Frankly, it hardly matters what you have—cold, flu or stomach flu—because everyone around you seems sick this time of year. Right?

While it is correct that your top priority when you’re sick is to get better, it actually does pay to figure out what you have. Kathy Mullins, RN, Systems Director of Infection Prevention for Trident Medical Center and Summerville Medical Center in Charleston, South Carolina, says understanding the differences between these common scourges of the fall and winter can help you treat yourself most effectively, recuperate quicker and avoid passing your germs to others.

What causes cold and flu
Although the common cold and flu are both viral infections that primarily affect the respiratory tract, they’re caused by different viruses. The cold is caused by a variety of viruses that includes rhinovirus, coronavirus and adenovirus, while the flu is caused by either influenza A or B viruses.

Both cold and flu can be spread through the air when people who are sick cough, sneeze or even talk. Airborne droplets that contain the virus can enter your body through your nose or mouth. You can also pick up these bugs by touching contaminated surfaces and then touching your eyes, nose or mouth.

Some symptoms overlap, some are distinct
It can be tricky to tease out a diagnosis of cold or flu based on your own symptoms, since there is considerable overlap between the two.

Both the cold and flu may entail sneezing, stuffy nose and sore throat, though those symptoms tend to be more common with the cold. Both ailments also often involve a cough, though chest discomfort that accompanies a cold is typically less severe than that associated with the flu. You may also feel fatigue or weakness with both cold and flu, but the severity tends to be greater with the flu.

Meanwhile, some of the flu’s hallmark symptoms—body aches, chills and headache—are largely unique to that affliction, as is fever. A fever associated with the flu tends to last three to four days, while fever is rare in adults with a cold.

Another clue you may have a flu rather than a cold is if your symptoms arrived all of a sudden. Cold symptoms tend to unfurl slowly, while a flu tends to hit you hard, quickly, and results in a more severe illness.

Although there are a variety of over-the-counter remedies available for cold symptoms, there are no treatments that attack the cold virus directly as anti-viral meds do for the flu.

Similarly, while there are flu vaccines available—which virtually everyone should get in the late summer or early fall, before flu season begins—there is no vaccine to reduce your chances of picking up the cold.

Cold, flu… what difference does it make?
In the best-case scenario, it really doesn’t matter whether you have a cold or flu, since each infection typically resolves on its own within about two weeks. But the stakes are much higher for flu, which can result in severe complications that may even become life-threatening.

If you’re otherwise healthy, it’s unlikely you’ll experience any adverse effects from the flu. But certain populations are at higher risk, including children under 5 years old, adults 65 and older, pregnant women, people with extreme obesity, folks living in nursing homes and people with certain medical conditions like chronic lung or heart disease, diabetes and those with weakened immune systems.

Flu testing and treatment
Most people without risk for flu complications don’t need to be tested for the flu, since their course of treatment—rest, treating fever with acetaminophen, drinking clear fluids—doesn’t differ appreciably from the way they’d handle a cold.

But some people at high risk may be tested to confirm a flu diagnosis, and a positive result may necessitate more aggressive treatment with a prescription antiviral drug like oseltamivir.

Because antiviral treatment tends to have the greatest benefit when started within 48 hours of getting sick and thus should begin as soon as possible, a doctor may not wait for test results to start treatment in high-risk individuals or may even prescribe treatment despite a negative result if the situation calls for it.

In certain cases, the flu may require emergency medical help. Call your doctor immediately or head to the ER if you experience:

  • Flu symptoms that seem to improve but then return with fever and a worsening cough
  • Difficulty breathing or shortness of breath
  • Pain or pressure in the chest or abdomen
  • Dizziness or confusion
  • Severe vomiting

Likewise, children or infants showing any of the following signs should receive immediate medical attention:

  • Fast breathing or difficulty breathing
  • Blue skin color
  • Not eating or drinking enough fluids
  • Not waking up from naps or not interacting
  • Excessive irritability
  • Fever with a rash
  • Crying without tears
  • Fewer wet diapers than normal

“If you’re unable to get your fever down or you become so sick you can’t care for yourself and you have no one to help you—particularly if you start vomiting or having diarrhea—you would definitely want to seek medical attention,” says Mullins.

Many of the symptoms associated with the flu—including fever and sweating, as well as less common symptoms such as loss of appetite, vomiting and diarrhea—can contribute to dehydrating the body, which is why the steady intake of fluids is so important when you have the flu. Staying hydrated aids your immune system’s fight against the virus, while dehydration can contribute to some of the flu’s more severe complications.

“Dehydration is more than being thirsty,” Mullins explains. “When your electrolytes become imbalanced and you become severely dehydrated, your organ function may be affected, your brain may be impaired. It can even lead to heart issues.”

Can you get the flu in your stomach?
Despite the name, the stomach flu is not an influenza virus that migrates into the gastrointestinal tract. Stomach flu is a misnomer and typically refers to viral gastroenteritis, an inflammation of the intestinal tract most commonly caused by norovirus, but sometimes also by rotavirus, astrovirus or enteric adenovirus. (Other forms of gastroenteritis may be caused by bacteria or parasites.)

Although viral gastroenteritis may sometimes yield generalized symptoms similar to those seen with the flu—headache, chills, aches, pains and fatigue—it doesn’t often cause fever, and if it does, it tends to be low-grade. Instead, symptoms tend to congregate in the gastrointestinal tract and may include diarrhea, nausea, stomach pain and vomiting. Adding to the confusion, influenza may occasionally also cause diarrhea or vomiting in adults (though these tend to crop up more commonly in children).

Stomach flu typically spreads through contaminated food or water, and you can also pick it up through contact with the fluids of with an infected person or by touching contaminated surfaces. Less commonly, the bug can be transmitted via droplets projected into the air via vomit, as opposed to the sneeze- or cough-borne particles that transmit the flu.

Although there are no anti-viral treatments to cure stomach flu, the good news is that viral gastroenteritis typically clears up within a day or two.

But as with the flu, dehydration is a concern, particularly since people with stomach flu lose fluids through vomiting and diarrhea. “You can become dehydrated very, very quickly,” says Mullins, “especially children.”

It’s therefore crucial to stay hydrated. If vomiting is an issue, it may help to drink small amounts of clear liquids (2 to 4 ounces) at a time. Water is the go-to, but you can also try rehydration drinks like Pedialyte or sports drinks like Gatorade to help replenish electrolytes.

Rest and fluids are typically all you need to recover, but if diarrhea lasts for more than a few days or becomes bloody, or if you experience any of the following signs of extreme dehydration, contact your care provider:

  • Confusion or dizziness
  • Dry or sticky mouth and throat
  • Decrease in urination or concentrated urine that looks dark yellow
  • Unusual sleepiness, fussiness or lack of tears when crying (typically seen in children)

Severe dehydration may require hospitalization and IV treatment.

“If you are so sick that you can't keep any food down, you have a fever greater than 104 degrees—or 102 degrees in children—that you can't break with Tylenol, or if you are unable to care for yourself, you need to seek medical attention so that you can get re-hydrated,” says Mullins.

“Depending upon how dehydrated you get,” Mullins notes, “gastroenteritis can be fatal.”

Steering clear of cold, flu stomach flu
Despite the differences in treatment approaches to cold, flu and stomach flu, there’s one simple preventive measure that helps for all three.

“Cold, flu and stomach flu are all very, very contagious,” says Mullins, “so I can't stress this enough: Wash your hands. Keep your hands away from your face. And for the flu, get the vaccine.”

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