Plus, how to prevent and treat the two viruses.
Flu vs. Cold
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Colds and the flu are often lumped in together, and for good reason. Not only do they both make you feel like crap, but there’s also the fact that the two respiratory illnesses like to rear their heads around the same time each year once temps begin to dip.

All of this means that when you’re feeling under the weather, it can be tough to tell what’s what. Is your sore throat the result of the common cold or influenza? And why are you so damn tired?

Luckily, even though the two illnesses share a lot of similarities, there are also some major differences that can help guide you toward the right treatment. Ahead, doctors share how exactly to tell if you have the flu or a cold, and what the best treatments are to knock ‘em out and feel better fast.

Here's how cold and flu symptoms differ:

While cold and flu symptoms overlap, there are some key differences to take note of, says Ali S. Raja, M.D., the executive vice-chairman in the Department of Emergency Medicine at Massachusetts General Hospital in Boston.

“Colds usually begin more gradually and rarely have fevers and body aches," he says. "If you've had a gradual onset of a sore throat, a stuffy nose, and generally just feel tired, you've probably got a cold.”

On the other hand, abrupt onset of fever, body aches, severe fatigue, a headache, and a cough, is likely the flu, Dr. Raja says.

Both the flu and common cold are viruses that can lead to moderate complications, like sinus and ear infections, but a common cold tends to be milder than the flu, and less dangerous. While it’s impossible to know exactly how many people die from the flu every year  — especially because it can lead to deadly complications like pneumonia, congestive heart failure, or other respiratory problems like chronic obstructive pulmonary disease (COPD) — the CDC estimaes that there were 34,200 deaths in the U.S. during the 2018–2019 flu season.

Needless to say, it’s much riskier to have the flu than to catch a cold (especially if you have a weak immune system, are elderly, pregnant, or a child), which is why the CDC urges people to get their flu shot every year.

And if you’ve been wondering: “Can a cold turn into the flu?” the answer is simple — nope. While the two illnesses are awful in their own ways, they are caused by different viruses, meaning there’s no chance the cold can become influenza.

How to prevent the flu and the common cold:

You’ve probably heard this one before, but it’s worth repeating. One of your top defense mechanisms for preventing the cold and flu is simple: Wash your hands and keep them away from your face to prevent the spread of germs.

“Washing your hands frequently, especially if you’re around people who are sick, will reduce the chance that you get sick too,” explains Nate Favini, M.D., a doctor and the medical lead at Forward, a preventive primary care service.

Dr. Favini says he also favors vitamin C as a means for keeping the common cold at bay. “I take 2,000 milligrams of vitamin C every morning and bump it to 3,000 milligrams if I’m feeling under the weather,” he says, noting that vitamin C supplementation can help reduce the severity and duration of the common cold.

As for the flu, there’s one measure that all doctors agree is crucial to reducing your risk of contracting the virus, and that’s the flu shot.

“Getting the flu shot is the smart thing to do for your own health — many people don’t realize that even healthy, young adults can get sick to the point of hospitalization or even death,” Dr. Favini says. “Beyond that, getting vaccinated contributes to what’s called 'herd immunity' — the more people that get vaccinated, the less likely a severe epidemic becomes.”

He added: “This helps protect more vulnerable people like young babies who can’t get the flu shot and seniors who are more likely to become very ill with the flu. Your shot could save the life of someone you know.”

Important to note: Docs recommend getting your flu shot ASAP (especially this year), but it's never "too late", Dr. Raja says. “Even if you’ve already had the flu this season, the shot can help prevent other strains, so go get one.”

And a few important measures you’ll want to take year-round to stop sickness in its tracks? Get plenty of sleep and drink lots of water. These are not just helpful life hacks; they keep your immune system strong.

How do I treat a cold or the flu?

When it comes to the common cold, symptoms will typically resolve within seven to 10 days (and you should reach out to your doctor if they don’t). In the meantime, there are a number of home remedies for cold symptoms, like popping zinc or probiotics, sipping on ginger tea, and taking elderberry supplements.

When it comes to OTC medications Dr. Favini says you won't find a cure-all, but you find relief through targeted symptoms, like acetaminophen or ibuprofen for a fever or headache, or a decongestant if your cold has lead to a less-than-favorable stuffy nose.

When it comes to the flu, many people can also wait it out at home, Dr. Raja says, however, there are some symptoms you simply shouldn't ignore. "If you can't stay hydrated or keep vomiting when you try to eat, have a fever that just won't go down with acetaminophen or ibuprofen, or start feeling confused or woozy, call your doctor, nurse practitioner, or physician's assistant," he says. "This is especially true for young children (under one) or older adults (over 65) — they should call if they start running any sort of fever at all."

There’s now a quick test to find out if you have the flu, and antiviral medications are most effective in the first 48 hours. (FYI, keep in mind most people with flu are contagious for about one day before they show symptoms.)

“If you can, continue to eat a balanced diet, rich in a variety of vegetables and fruits,” Dr. Favini adds. “And increase your intake of soups, which replenish electrolytes and fluids.” And of course, in both instances, hydrating and getting lots of rest are key — so go ahead and cue up some Netflix.