7 Times You May Think You Have the Flu—but Don’t

Updated: Mar. 17, 2022

When those nasty symptoms set in, they might signal the flu—or something else entirely. Here's how to tell the difference.

It’s the sick season

Flu season is here. For vulnerable people like children, the elderly, and those with lung ailments such as asthma and cystic fibrosis, classic flu symptoms such as a sudden fever, muscle aches, fatigue, or a dry cough can be cause for serious concern. But not every flu-like symptom signals the flu. Many other illnesses can prompt the same symptoms, says Sean Cloonan, MD, an internist and infectious disease specialist at Scarsdale Medical Group in Scarsdale, New York. Here’s a rundown of seven copycat conditions that could make you think you have the flu.

Sick african american girl working from home office. Ill young black woman with cold, sitting at desk with laptop computer and sneezing for allergy.
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The common cold can also bring on a cough and fatigue, but it’s caused by different viruses than those that cause the flu, says Dr. Cloonan. The flu tends to be more intense than a cold, according to the Centers for Disease Control and Prevention (CDC)—though a cold typically lasts longer (seven to ten days versus three to five days for the flu); you’ll get a stuffy or runny nose, as well. These are the textbook scenarios, says Dr. Cloonan, “but real life doesn’t always follow a textbook, and someone who seems to have a cold can actually be fighting off influenza.” The only way to definitively tell the difference is to be tested for the flu. Don’t miss these 50 ways to avoid catching a cold this season.

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Strep throat

You’ll also get a fever and a general feeling of malaise with strep, says Dr. Cloonan. But the intense pain in your throat along with redness and, sometimes, white spots on your tonsils are all strep throat symptoms that distinguish this infection from the flu. While the flu is caused by influenza viruses, strep throat is caused by a specific type of bacteria called group A Streptococcus, or group A strep. If you think you may have strep throat, see your doctor for testing and, if it’s positive, a prescription for antibiotics. Strep throat should be treated because in some cases it can lead to complications like rheumatic fever, which is a condition that can affect the heart and lead to rheumatic heart disease. However, antibiotics are useless for the flu because it’s caused by a virus, not bacteria.

Young asian woman coughing and sitting on her bed,Concept of health


Infectious mononucleosis–dubbed “the kissing disease“—can mimic the flu, “though there’s no seasonality to it,” says Dr. Cloonan. Most commonly caused by the Epstein-Barr virus, the illness usually brings on a fever, fatigue, sore throat, and swollen lymph nodes in the neck and other parts of the body; nearly nine out of 10 people will get sick with this virus at some point in their life. “The younger you are when you’re exposed to it, the less sick you tend to get,” he says. “You may not know a young child has it because kids are sick so often and the illness may not be severe.” Catch mono as a teenager or an adult, and you’ll really know it—the symptoms will lay you low. “You don’t see many adults with mono because most of us have had it already.” Be sure you know the 11 silent signs of mono.

Baby legs in the odeal
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Respiratory syncytial virus—RSV, for short—is an infection of the respiratory tract that may seem like a cold or the flu that’s easily spread through coughing and sneezing. Symptoms include fever, nasal congestion, a barking cough, difficulty breathing, and lethargy. “The virus causes the most trouble for very young children in the first year of life,” warns Dr. Cloonan. Call a doctor if your child exhibits these symptoms.

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“Influenza is dangerous, but the flu itself almost never kills anyone,” says Dr. Cloonan. What’s deadly is when the infection turns into bacterial pneumonia—an infection that inflames the air sacs in one or both lungs. A common scenario: Someone with the flu starts to feel better, but then a second wave hits. “That’s bacterial pneumonia,” says Dr. Cloonan. “If the fever goes away and comes back, you should be concerned that the pneumonia happened after the flu has run its course.” In addition to fever, symptoms include a cough that starts out dry and progresses to wet, often with blood or mucus. See your doctor immediately, Dr. Cloonan advises—”You will probably need antibiotics.” Viral pneumonia can also occur separately from the flu. This version is usually milder than bacterial pneumonia, with symptoms like a cough, congestion, and fatigue. Don’t miss these 7 signs your upper respiratory infection is actually pneumonia.

Sick woman on the bed blowing her nose


This inflammation of the membranes that protect the brain and spinal cord can be caused by a virus or bacteria, according to the CDC. Both have symptoms similar to the flu, including fever and fatigue, but meningitis also causes a stiff neck and sensitivity to bright light. The viral form is less severe, and people who get it often recover on their own. Bacterial meningitis, however, can be deadly and requires immediate medical attention.

Chest x-ray.


This illness not only looks and feels like the flu—with coughing, lethargy, a sore throat, and sometimes a low fever—but is caused by many of the same viruses. The difference is that it targets the chest and throat rather than triggering full-body aches, and the cough can last up to three weeks and sometimes longer. There’s no test for bronchitis, but doctors can diagnose it through a physical exam. A doctor may also order a chest x-ray to rule out pneumonia.

Learned focused therapist examining patients lungs
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When to call a doctor

“When you are hit with a sudden fever or a cough that feels really bad, contact your doctor,” says Dr. Cloonan. Time is of the essence, he says, because if you do have the flu and are prescribed medication such as Tamiflu, it will work only if you begin taking it within 48 hours of the first symptoms. If you don’t have the flu, your doctor can diagnose what you do have and recommend a course of treatment. Check out these 13 household items that increase your risk for colds and flu.

Asian woman is taking vaccine shot on her shoulder.
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The importance of the flu shot

“The influenza vaccine isn’t perfect, but it’s the only one we’ve got,” says Dr. Cloonan. “Other than washing your hands and not exposing yourself to people who are sick, the shot is the best way to lower your risk and also lessens symptoms if you do get the flu.” The CDC recommends a flu vaccine every year for everyone over the age of six months of age; taking this measure can reduce the risk of a child dying from the flu. Dr. Clooney adds that people over the age of 65 and anyone with chronic medical problems such as diabetes and chronic pulmonary obstructive disease should also receive the pneumococcal vaccine. Next, find out the things you shouldn’t do if you do have the flu.