10 Conditions With Flu-Like Symptoms

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  • If we haven’t had the flu (influenza) ourselves, we all know someone who has—the aching body, cough and fever—a week or longer of feeling like we’re slugging through mud and hoping desperately to feel better. But there are many illnesses that initially cause flu-like symptoms, some of which may be more serious if left untreated. But how can you tell when you should see a doctor for flu symptoms? Here are a few of the more common illnesses that can mimic flu symptoms.

  • 1
    The Common Cold
    Man sneezing

    Whether it’s a summer cold or a winter cold, colds often bring along their share of misery. A particularly bad cold could mimic some flu symptoms. These include having a runny and/or stuffed up nose, coughing, feeling like your chest is congested, even a sore throat and headache. In adults, fevers are rare in colds, but you could have a low-grade one. Children do tend to have more fevers with colds though. Unlike the flu, however, colds don’t cause muscle aches. And, cold symptoms go away in about a week, usually, while flu symptoms can last much longer.

  • 2
    Meningitis (Bacterial or Viral)
    male-holding-neck

    Meningitis is a serious infection or inflammation of the meninges. These are the membranes that surround and protect your brain and spinal cord. A sudden high fever and headache could make people think they have a bad flu, but it is vital you get medical help as quickly as possible if you experience any of these other symptoms as well: stiff neck, severe headache with nausea and vomiting, eyes sensitive to light, seizures, confusion, difficulty balancing or walking, or a skin rash.

  • 3
    Sepsis
    Woman with fever, cold or flu drinking tea in bed

    Sepsis, what used to be called blood poisoning, is your body’s overreaction to an infection. As your body fights the infection, something goes wrong and your body begins to attack itself instead. Sepsis can be fatal, but it’s easy to miss the signs and symptoms or to mistake them for the flu. If you’ve recently had a medical procedure, you’ve injured yourself, or you’ve been ill, watch for these symptoms: fever (although you could have a lower than normal body temperature), confusion or grogginess, feeling extremely sick or extreme pain. If you think you may have sepsis, get medical help quickly.

  • 4
    Pneumonia
    Young Caucasian man wrapped in blanket on couch with cough due to cold or pneumonia

    Pneumonia, whether it’s bacterial, viral or fungal, can initially be confused by the flu virus. Pneumonia symptoms can include a productive cough (bringing up green or yellow sputum), shortness of breath, fever, chills, and pain in your chest. As with the flu, you could also have no desire to eat anything, you maybe fatigued. A sense of confusion is also possible. The clue is how you are coughing and what you are coughing up. If the color of the sputum changes, you develop chest pain, and/or your fever continues to climb or doesn’t go away, you might have pneumonia.

  • 5
    Blood Cancer
    man-giving-blood

    People can have blood cancer for a while before they are diagnosed. This is because symptoms can be vague and, in the early stages, mistaken for something much less serious like the flu. These symptoms may include fever, persistent cough, no appetite, fatigue, chills and sweating, particularly at night. If you have these symptoms and they aren’t going away, see your doctor as soon as you can to rule out a serious illness like leukemia or lymphoma. Other blood cancer symptoms include persistent fatigue, unintended weight loss, recurring nosebleeds, swollen lymph glands, and bone pain.

  • 6
    Lyme Disease
    Close-up of tick on fingertip

    Lyme disease is becoming increasingly common in the United States. Doctors don’t have exact numbers because not everyone who’s infected sees a doctor, but about 30,000 cases are reported each year. This disease, caused by a bite from an infected tick, can cause flu-like symptoms (fever, chills, headache, fatigue, body aches, and swollen lymph glands). If you don’t see the bite, it’s easy to think it is just the flu. However, if you’ve been in an area where you could have received a tick bite, examine your skin to see if there are any red spots or a rash. This may be due to a tick bite. See a doctor to be safe.

  • 7
    Mononucleosis—or the ‘Kissing Disease’
    Sore throat exam

    Mononucleosis is caused by Epstein-Barr virus and is spread through contaminated saliva—sharing drinks, utensils, or through intimacy. While the infection itself isn’t usually serious, it can cause serious complications. Signs of mononucleosis include fever, sore throat, fatigue, and swollen lymph glands. Symptoms that would not be mistaken for the flu include swollen tonsils, skin rash, and a swollen spleen. It can take from 4 to 6 weeks after exposure to the virus for the symptoms to appear, which is why the symptoms may be mistaken for the flu at first—the infected person may not remember being exposed to someone with mononucleosis.

  • 8
    Cat-Scratch Disease
    Young Caucasian woman doing plank exercise or yoga in apartment with cat next to her

    Most cat scratches do little more than draw some blood and cause a bit of pain. However, these scratches, as well as cat bites, can cause a bacterial infection called cat-scratch disease (Bartonella henselae infection). People who contract cat-scratch disease require rapid antibiotic treatment to prevent complications. Signs and symptoms include fever, headache, fatigue, and a poor appetite. If you’ve been scratched or bitten by a cat and you have these symptoms, in addition to redness or swelling around the injury, seek medical help.

  • 9
    Rocky Mountain Spotted Fever
    tired male backpacker with dehydration and heat exhaustion

    Rocky Mountain spotted fever is a tick-borne infection like Lyme disease. However, RMSF is much more serious and can lead to serious complications without treatment. See your doctor as soon as possible if you have been in an area where you may have been bitten by a tick or you know you have been and you experience any of these symptoms: fever, headache, muscle pain, nausea and vomiting, poor appetite, and stomach pain. A rash may develop 2 to 4 days after you notice the fever.

  • 10
    Babesiosis
    woman on couch sick with fever, cold or flu

    Another disease caused by ticks, babesiosis is a parasitic disease most commonly found in the Northeast and Midwest parts of the United States. It can be life threatening. Although rare, the disease can also be spread through contaminated blood donations and from mother to child during pregnancy and delivery. As with the other illnesses discussed, babesiosis can cause fever, chills, sweats, headache, muscle aches, nausea, lack of appetite and fatigue. If you have these symptoms and they are not going away, and you believe you may have been bitten by a tick, see your doctor for blood tests.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Nov 10
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Sepsis. Sepsis Alliance. http://www/sepsis.org
  2. Influenza (flu). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/flu/symptoms-causes/syc-20351719
  3. Meningitis. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/meningitis/symptoms-causes/syc-20350508
  4. Pneumonia Symptoms and Diagnosis. American Lung Association. https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/pneumonia/symptoms-and-diagnosis.html
  5. Cancer symptoms. Cancer Treatment Centers of America. https://www.cancercenter.com/cancer-symptoms
  6. Signs and Symptoms of Untreated Lyme Disease. Centers for Disease Control and Prevention. https://www.cdc.gov/lyme/signs_symptoms/index.html
  7. Lyme Disease. Centers for Disease Control and Prevention. https://www.cdc.gov/lyme/datasurveillance/index.html
  8. Cat-Scratch Disease. Centers for Disease Control and Prevention. https://www.cdc.gov/healthypets/diseases/cat-scratch.html
  9. Rocky Mountain Spotted Fever. Centers for Disease Control and Prevention. https://www.cdc.gov/rmsf/index.html
  10. Parasites – Babesiosis. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/babesiosis/index.html