If you feel lousy all of a sudden, that's a big clue.

By Madeleine Burry
December 04, 2018

There's nothing pleasant about being sick—and that’s particularly true if you get the flu or pneumonia, which can leave you feeling absolutely miserable. And, since the two debilitating diseases have a similar constellation of symptoms (think: fever, cough), it can be hard to know if it's pneumonia or flu.

Hard, but not impossible. And worth knowing, since it helps determine when (and if) you head to the doctor's office. Get must-know details on how to distinguish between pneumonia and the flu, along with the best way to avoid contracting both.

RELATED: 8 Signs Your Cough Could Actually Be Pneumonia

What are your precise symptoms?

“A headache and diffuse muscle aches and pains are much more common with flu than with pneumonia,” says Roger Lovell, MD, an infectious disease specialist at Piedmont Athens Regional Medical Center. Other common flu symptoms: a sore throat, stuffy nose, gastrointestinal symptoms (like vomiting or diarrhea), and coughing.

A cough is also a major symptom of pneumonia, but it has a different nature. A pneumonia cough tends to be productive, bringing up dark-colored phlegm that may contain blood, says Dr. Lovell. Pneumonia is characterized mainly by respiratory symptoms, says Joshua Scott, MD, primary care sports medicine physician at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles—that includes shortness of breath or difficulty breathing.

If it’s the flu, symptoms are usually far more severe, says Dr. Scott.

How quickly did your symptoms show up?

It’s very common for flu symptoms—fever, muscle aches, stuffy nose, sore throat, etc.—to arrive so suddenly that it’s possible to pinpoint the exact moment all your misery began, says Kimberly Brown, MD, MPH, an emergency medicine doctor in Memphis.

Pneumonia, in contrast, typically has a less dramatic entry, with symptoms ramping up over several days, says Dr. Lovell.

RELATED: Bronchitis vs. Pneumonia: How to Tell the Difference

What does your doctor say?

Seeing tons of patients gives doctors a knack for knowing which disease is which. “Sometimes patients come in and they just look like the flu,” says Dr. Brown—the air of misery, along with the runny nose, is a giveaway even before she asks about symptoms.

Doctors also use diagnostic tools. Listening to the lungs or taking a chest X-ray can reveal signs of pneumonia.

“There is a nasal swab test that can determine if you have the actual flu virus,” says Dr. Scott.

When it comes to viruses—either viral pneumonia or the flu—there’s not much doctors can do to help, with one big exception. If you have the flu, and get to the doctor right after you notice your symptoms, your doctor may prescribe an antiviral medication—like Tamiflu—to lessen the course and severity of symptoms, says Dr. Scott.

The catch? Antivirals are only effective if you use them ASAP—within one to two days of the onset of symptoms. And taking Tamiflu isn’t necessarily a pleasant experience; side effects can include nausea, vomiting, diarrhea, and dizziness. “The side effects may be worse than your actual flu symptoms!” says Dr. Brown.

Even if you miss the window for antivirals, it’s still worth it to get a diagnosis, says Dr. Scott. A doctor’s visit is an opportunity to rule out complications of the flu or the possibility you have another disease (like pneumonia), he says. And, if you have vulnerable members in your home—like an elderly person, for instance—they might want to take Tamiflu as a preventive measure, he says.

And what about if you think you have pneumonia? That's trickier. You'll need to visit the doctor if you have bacterial pneumonia to get a prescription for antibiotics. That's not necessary for viral pneumonia, which you mostly have to wait out while treating the symptoms.

Dr. Brown's advice: "If you are concerned about any of your symptoms, you should see a physician right away."

If it turns out you have either viral pneumonia or the flu (and didn't take Tamiflu), doctors typically recommend supportive care: Rest up, drink lots of fluids, and manage your symptoms with over-the-counter medications. Consider this further evidence that your grandma’s advice to have some chicken soup when you're feeling under the weather is sound policy.

RELATED: 13 Home Remedies for Bronchitis That Might Finally Ease Your Cough

Common sense—and vaccinations—are the best prevention tactics

The flu is one of the viruses that can cause pneumonia, says Dr. Lovell. Here’s why: All of those secretions from your stuffy nose, combined with the dehydration that often accompanies the flu, create an environment where bacteria can multiply too fast for your body to defeat, potentially leading to bacterial pneumonia, explains Dr. Scott.

If you didn’t get a flu shot yet, head to the doctor’s office or pharmacy stat. “Vaccinations for both the flu and pneumonia save lives and decrease hospitalizations,” says Dr. Lovell.

For healthy people, a flu shot reduces your chances of getting the flu, says Dr. Scott. And while it’s still possible to get the flu even after a vaccination, the shot will lessen both symptoms and how long the flu lingers, Dr. Scott says. Vaccines can also help prevent the most common cause of bacterial pneumonia, says Dr. Lovell. (These are usually recommended for young children, older adults, and people with certain underlying health conditions.)

Along with getting vaccinated, consider having a hands-off policy during this germ-heavy season, avoiding hugs and handshakes, says Dr. Scott, and wash your hands frequently (and especially after handshakes). This will help you avoid getting sick. Wipe down potentially germ-covered surfaces at home and work, says Dr. Brown. And, adds Dr. Lovell: Drink lots of water and maintain good nutrition.

RELATED: Why Do Some People Die From Pneumonia?

The bottom line

Wash your hands and get vaccinated for the flu (and check with your doctor about pneumonia vaccinations) to ward off these two diseases.

And if you are generally in good health and under 65, don’t get overly stressed if those preventive measures don’t work and you do contract the flu or pneumonia. Both diseases can be very serious, says Dr. Brown, but, she adds, “the vast majority of healthy people do well with treating the flu or pneumonia outside of the hospital.”

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