I have the flu. Can it turn into pneumonia?

Flu season brings coughs and fever. Beware of worsening symptoms of pneumonia.

Author: Sara Thompson

Published: February 4, 2025

Estimated reading time: 4 minutes

Influenza, or the flu, is a common respiratory infection caused by a virus that infects the nose, throat and lungs. Most people can clear the flu on their own. Sometimes there are complications of the flu, such as pneumonia. Pneumonia is an infection in the air sacs of one or both lungs and can be caused by viruses, bacteria or fungi. 

Influenza symptoms and risks

The flu is common in during certain times of the year. This is called flu season. The North American flu season typically occurs from October to May. During this time, respiratory infection rates are high, and more people are at risk of catching and spreading these illnesses. Influenza is different from stomach flu, which commonly causes nausea, vomiting and diarrhea. 

The most common flu symptoms are:

  • Fever
  • Cough
  • Muscle aches
  • Fatigue
  • Chills and sweating
  • Fatigue

It spreads through tiny droplets that come out of our mouths or noses when we speak, cough or sneeze. It may be possible to get the flu from touching a contaminated surface.

There are almost 3 million cases of flu each year in the United States, and thousands of flu-related deaths. Some factors may increase your risk for experiencing complications, including:

  • Pregnancy
  • Age
  • Asthma
  • Chronic lung disease, such as cystic fibrosis or chronic obstructive pulmonary disease (COPD)
  • Heart disease
  • Obesity; a body mass index (BMI) over 40

Pneumonia symptoms and causes

There are more than 30 causes of pneumonia, which are grouped by type. The types are:

  • Bacterial pneumonia. The most common is Streptococcus pneumoniae. This type of illness is more common if you have compromised immunity or poor nutrition or are of advanced age. While bacterial pneumonia can affect anyone, those at higher risk include people who abuse alcohol or smoke cigarettes, have a respiratory disease or viral infection, or have another illness. 
  • Viral pneumonia. Various viruses can cause this type, including the influenza virus, and it is responsible for about one-third of all pneumonia cases. If you have viral pneumonia, you may be more likely to develop bacterial pneumonia. 
  • Mycoplasma pneumonia. This type is caused by the Mycoplasma pneumoniae bacterium. It has somewhat different symptoms and physical signs. 
  • Other pneumonias. Less common pneumonias have other causes such as certain fungi. Atypical pneumonia is a less-severe type of this illness and is sometimes referred to as walking pneumonia. 

Symptoms of pneumonia include:

  • Cough, which may produce phlegm
  • Fatigue
  • Sweating or chills
  • Chest pain when you breathe or cough
  • Nausea, vomiting or diarrhea
  • Shortness of breath
  • Fever.

Can flu turn into pneumonia?

Pneumonia is a common complication of flu. The body’s immune system has been working to combat the flu, and that weakens its ability to fight off another illness. The highest-risk groups are children under 5, adults over age 65, pregnant people, and those with chronic medical conditions or an otherwise weakened immune system. Normally, flu symptoms can be treated at home, but you should be aware of worsening symptoms. 

You are also more likely to develop pneumonia after flu if you smoke, have asthma or diabetes, or have a BMI over 40.

If your flu symptoms are not getting better, be cautious, especially if you have another chronic condition or have compromised immunity. Pneumonia symptoms may develop a few days after flu symptoms and may appear to mimic flu symptoms. Seek immediate medical attention for:

  • A persistent, worsening cough with mucus
  • Severe chest pain
  • Difficulty breathing
  • A bluish tinge to the lips or fingertips
  • A very high fever

Preventing the flu and pneumonia

There are vaccines for both the flu and pneumonia. It’s important to get a flu vaccine every year, as the virus changes and flu shots are reformulated for strains expected to be most prevalent. Talk to your doctor about the pneumonia vaccine to see if you should get one and how often. Other ways to prevent the flu, besides vaccines, include good hygiene — such as hand-washing and covering coughs and sneezes. Also, boosting the immune system can reduce infection risk. This includes exercise, a healthy diet and good sleep.

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