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How Does the Flu Become Pneumonia?

Flu not going away? You might have pneumonia. Find out more.
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Last updated May 6, 2024

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What is the difference between the flu and pneumonia?


Pneumonia is an inflammation of the lungs due to an infection caused by bacteria, a virus, or a fungus. It can also be caused by aspirating (inhaling) food into the lungs.

The main symptoms are respiratory:

  • Cough
  • Trouble breathing
  • Chest congestion
  • Chest pain

You may also have generalized symptoms like fever, fatigue, and body aches.

Flu (influenza)

The flu is a respiratory illness caused by the influenza virus. It infects the nose, throat, and sometimes the lungs.

The main symptoms include

Some of the symptoms of flu and pneumonia overlap so it can sometimes be difficult to tell the difference. The flu can also lead to pneumonia.

If you get pneumonia from having the flu, it can be very serious, especially if you are considered high risk.

How does the flu become pneumonia?

Pro Tip

The flu vaccine cannot cause the flu illness. However, some people may experience mild flu-like symptoms. This is likely due to your body mounting an appropriate immune response, which will help you fight an infection if you are exposed to it. Either way, these mild symptoms are better than developing the flu and it’s possible complications including pneumonia. —Dr. Chandra Manuelpillai

The flu can weaken the immune system and trigger an inflammatory response in your body. This makes you more susceptible to getting other infections.

Pneumonia may be a complication of the flu virus. Or you may get a secondary infection with a bacteria or other virus.

If you have the flu, it can be difficult to know if you have developed pneumonia as well. Often it feels like your respiratory symptoms are getting worse. Sometimes people will say they feel better, but then suddenly their symptoms worsen. These symptoms include difficulty breathing, chest pain, or worsening cough.

Just because you have the flu, it does not mean you will develop pneumonia. Your doctor will likely be able to diagnose your pneumonia with a chest X-ray.

Some people have a higher risk of developing pneumonia:

  • Those with a weakened immune system.
  • Older adults.
  • Children.
  • Those on medications that weaken the immune system (including chronic steroids, chemotherapy, or post-transplant medications).
  • People with lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis.
  • Smokers.
  • People with other medical problems such as heart disease, diabetes, liver disease, and HIV.

How is pneumonia treated?

Flu-related pneumonia may be caused by the flu virus itself (viral pneumonia) or a secondary bacterial infection (bacterial pneumonia).

There is no specific treatment for viral pneumonia. Treatment is focused on reducing symptoms:

  • For fever and pain, take over-the-counter acetaminophen (Tylenol) or ibuprofen (Advil, Motrin).
  • Take cough suppressants.
  • Use nasal decongestants and/or nasal saline drops, spray or rinse to relieve congestion.
  • You can also use a humidifier for congestion.
  • Increase fluid intake (tea, soup, etc.).
  • Get enough rest.

For bacterial pneumonia, you’ll be given antibiotics. It is important to finish all the antibiotics, even once symptoms start to improve, so that the infection doesn’t return.

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How serious is flu-related pneumonia?

Pro Tip

While high-risk people are at an increased risk of complications and death from flu and flu-related pneumonia, healthy and young people are also at risk. So again, prevention methods cannot be emphasized enough. Also, early detection and management can be life-saving. —Dr. Manuelpillai

Pneumonia in high-risk people is always considered serious because of the risk of complications and their difficulty with fighting the infection. Since the immune system is already compromised by the flu, flu-related pneumonia can be more serious.

If you’re high-risk, you may need to be hospitalized for close monitoring and treatment. You may need to be put on oxygen or a ventilator, or take stronger antibiotics.

Pneumonia can also lead to complications such as lung abscess, inflammation of the heart, and stress on the kidneys. These are all very serious and life-threatening complications.

When to call your doctor or go to the ER

Most healthy people will be able to care for their flu and pneumonia symptoms at home on their own. However, if you are concerned, call your doctor or go to urgent care (one that can perform X-rays) for an evaluation.

You should get emergency care if you have multiple symptoms: severe difficulty breathing, heart racing, dizziness, and vomiting.

Call 911 immediately if any of these symptoms are severe or you have symptoms of low oxygen (blue discoloration) or chest pain.

How do you prevent getting pneumonia from the flu?

Pro Tip

Vaccinations are the best way to prepare your body to fight both the flu infection and its complications. —Dr. Manuelpillai

Avoid getting sick in the first place

The same strategies to prevent the flu will prevent flu-related pneumonia. This includes:

  • Avoiding close contact with sick people.
  • Frequent hand washing.
  • Not smoking and avoiding secondhand smoke.

Get vaccines

It’s important to stay up-to-date with your vaccinations, including your flu shot. You should get one every year—strains change year-to-year, which is why you need a new shot each fall.

Also, get any recommended pneumococcal vaccinations (these specifically prevent pneumonia caused by Streptococcus pneumoniae bacteria). The vaccines help protect against many types of pneumococcal bacteria that most commonly cause serious infections in children and adults.

Pneumococcal vaccines are recommended to high risk individuals, children younger than 5, and adults 65 and older.

Take Tamiflu

Some research suggests that if you are high-risk and get the flu, you should be prescribed oseltamivir (Tamiflu), an antiviral medication. If you take it within the first 2 days of symptoms, it may decrease how long you’re sick and your chance of complications.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Manuelpillai is a board-certified Emergency Medicine physician. She received her undergraduate degree in Health Science Studies from Quinnipiac University (2002). She then went on to graduated from Rosalind Franklin University of Medicine and Sciences/The Chicago Medical School (2007) where she served on the Executive Student Council, as well as was the alternate delegate to the AMA/ISMS-MSS G...
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