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Conditions With Flu-Like Symptoms

Medically Reviewed by Michael W. Smith, MD on May 03, 2021

When you’re feeling run-down, feverish, and achy, you might wonder if you have the flu. You’re more likely to catch it in the fall or winter, especially if you haven’t gotten a flu shot.

Flu symptoms tend to hit suddenly. You might have some or all these signs:

But other health conditions can bring on the same. So how can you tell if it’s the flu or something else? Your doctor would need to do tests to know for sure. But here are a few conditions that also cause flu-like symptoms.

The Common Cold

Like the flu, a cold can wear you down and make you cough, sneeze, and cause a sore throat. Still, a few key clues may help you tell these viral illnesses apart. Colds usually come on slowly, and the symptoms tend to be milder. You’re more likely to get a runny or stuffy nose. But you’re far less likely to run a fever or have body aches.

COVID-19

This highly contagious and potentially deadly disease is caused by a different virus than the flu. Both COVID and the flu spread from person to person, mainly through:

  • Coughing
  • Sneezing
  • Talking close to someone else

And they both can lead to life-threatening health problems, like pneumonia and respiratory failure. But there are important differences. COVID-19 appears to:

  • Spread more easily than the flu
  • Make you contagious longer than the flu does
  • Cause worse illnesses in some people

It can also change or steal your sense of taste or smell. If you’re 16 or older, it’s important to get the COVID-19 vaccine as soon as possible.

HIV

The virus that causes AIDS can bring on flu-like symptoms about 2 to 4 weeks after you get infected. Some of the early possible signs of an HIV infection are:

  • Fever and chills
  • Muscle pain
  • Sore throat
  • Headache
  • Tiredness
  • Diarrhea

HIV infection can also cause unrelated symptoms, like:

Lyme Disease

Deer ticks trigger this bacterial infection when they bite you. Symptoms include:

  • Fever
  • Chills
  • Muscle soreness
  • Tiredness

Unlike the flu, Lyme disease can cause a rash where the tick bit you. It may be shaped like a bull’s-eye with one or more reddish rings. Some people with Lyme disease also have drooping of the face, or Bell’s palsy.

Encephalitis

This is inflammation in your brain. It’s common for encephalitis to cause:

  • Headache
  • Fever
  • Achy muscles
  • Tiredness

Encephalitis can also bring on:

  • Agitated feelings
  • Hallucinations
  • Seizures
  • Loss of feeling or movement in certain body parts
  • Trouble talking or hearing
  • Unconsciousness or coma

Babies or young children with encephalitis may also have symptoms like:

  • Stiff body
  • Not feeding much or not waking up to feed
  • Throwing up
  • Cranky behavior
  • Bulges in soft parts of the baby’s skull

Meningitis

This condition inflames the thin coverings that protect your brain and spinal cord. The flu virus is one of several things that can lead to meningitis, including other viruses and bacteria.

Some of the early symptoms of meningitis can seem like the flu. For instance, you may run a sudden high fever and get a headache with nausea or vomiting.

Other meningitis symptoms include:

Adenoviruses

These common viruses aren’t the same as the ones that cause the flu, but they can bring on flu-like symptoms. Both illnesses can lead to health problems like pneumonia and bronchitis, too.

Adenoviruses can cause pinkeye and (less often) bladder infections. They can also trigger conditions that affect the brain and spine. Although the two infections spread similarly, adenoviruses may cling to commonly touched surfaces longer. Disinfectants may not fight them as well.

Pneumonia

This common lung infection can range from mild to severe. The flu virus is one of several things, including bacteria and fungi, that can cause it. The symptoms can look a lot alike. With pneumonia, you could have a cough, fever, chills, fatigue, and trouble breathing.

But pneumonia doesn’t come on as fast as the flu, and it’s not likely to make your muscles ache. You’re more likely to have these symptoms, too:

  • Blue-colored fingernails and lips
  • Chest pain when you breathe deeply or cough
  • Cough with bloody mucus
  • Fast or shallow breathing

Carbon Monoxide (CO) Poisoning

This can happen when carbon monoxide gas builds up indoors and makes you sick when you breathe it in. It can set off tiredness, nausea or vomiting, dizziness, and headache. Carbon monoxide poisoning is an emergency. If you breathe in too much, you could pass out and die.

Buying a carbon monoxide detector and getting a technician to check your heating systems and fuel-burning appliances once a year are two things you can do to make your home safer.

WebMD Medical Reference

Sources

SOURCES:

CDC: “When Is Flu Season?” “Influenza (Flu): Diagnosis,” “The Difference Between Cold and Flu,” “Adenoviruses,” “Carbon Monoxide Poisoning: Frequently Asked Questions,” “Meningitis,” “Vaccine Considerations for People with Disabilities,” “What is the difference between Influenza (Flu) and COVID-19?”

American Lung Association: “Pneumonia Symptoms and Diagnosis,” “What Causes Pneumonia?”

Cedars-Sinai: “What Is Adenovirus?”

Piedmont Healthcare: “The difference between pneumonia and the flu.”

Mayo Clinic: “Bronchitis,” “Meningitis,” “Encephalitis.”

Lymedisease.org: “Lyme Disease Symptoms,” “Early Lyme Disease.”

UpToDate: “Patient education: Lyme disease symptoms and diagnosis (Beyond the Basics),” “Patient education: Symptoms of HIV infection (Beyond the Basics).”

HIV.gov: “Symptoms of HIV.”

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