Pneumonia causes

Types of pneumonia: causes, symptoms and treatments

Pneumonia is a type of lung infection that causes the air sacs in the lungs to fill with fluid.

There are different types of pneumonia. In most cases, pneumonia is caused by a bacterial or viral infection. In rarer cases, pneumonia can be caused by inhaling fluid into the lungs or by a fungal infection.

However, healthcare providers are not always able to identify a cause of pneumonia: one study found that in up to 62% of pneumonia cases, no pathogen such as a virus, bacteria or fungus is not identified.

When people discuss the types of pneumonia, they also consider the severity of the infection. For example, walking pneumonia is a non-medical term used to refer to a mild case of pneumonia, where the patient may still be standing and walking. People also distinguish cases of pneumonia based on where they were collected: for example, hospital-acquired or community-acquired pneumonia.

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Viral infections are one of the most common types of pneumonia. About 27% of patients with pneumonia have an identifiable viral cause. Viruses that affect the airways can cause inflammation of the lungs and lead to pneumonia.


The most common viruses associated with viral pneumonia are:

If you have any of these viral infections, in most cases you will not develop pneumonia. However, if you start to experience symptoms of pneumonia, such as shortness of breath or a gray or blue tinge on the skin, you should contact your healthcare professional.


Viral pneumonia infections are usually mild, and most people recover without medical intervention within two to three weeks.

If you have viral pneumonia, you need to get enough sleep and drink plenty of fluids. Antibiotics will not work for viral pneumonia, although in some cases your healthcare professional may prescribe an antiviral medicine such as Tamiflu (oseltamivir), Relenza (zanamivir), or Rapivab (peramivir).

Having viral pneumonia can increase your risk of developing bacterial pneumonia, which is often more serious.


A bacterial infection can also lead to pneumonia. The Centers for Disease Control and Prevention (CDC) found that 14% of patients with pneumonia had an identifiable bacterial cause. Bacterial pneumonia can develop on its own or after a person has had viral pneumonia.


Common causes of bacterial pneumonia include:

  • Streptococcus pneumoniae: This bacteria causes pneumococcal disease and is the most common cause of bacterial pneumonia.
  • Legionella pneumophila: This bacteria thrives in man-made water systems, including hot tubs, plumbing systems, and cooling towers. It leads to a serious type of pneumonia known as Legionnaires’ disease.
  • Mycoplasma pneumoniae: This type of bacteria is common in crowded living spaces like dorms and prisons. It leads to a mild infection often called foot pneumonia.
  • Chlamydia pneumoniae: This type of bacteria usually causes mild pneumonia, most commonly in people over 40.
  • Haemophilus influenzae: This type of bacteria is more likely to cause pneumonia in people with existing lung diseases, such as cystic fibrosis and chronic obstructive pulmonary disease (COPD).


Bacterial pneumonia can be treated with antibiotics such as Zithromax (azithromycin), Biaxin (clarithromycin) or Erythrocin (erythromycin). It is important to take your medications as prescribed and to let your healthcare professional know if your symptoms change.


Bacterial pneumonia can be serious and lead to complications, including bacteremia, a bacterial infection of the blood also known as septic shock. Bacterial infections can progress quickly, so don’t hesitate to seek help if your symptoms get worse.


Foot pneumonia is a type of bacterial infection also known as mycoplasma pneumonia. This type of pneumonia is mild and you can usually continue with your daily activities when you have it, hence the name foot pneumonia. Walking pneumonia often spreads in crowded living spaces, such as dormitories or prisons.


The most common symptom of foot pneumonia in adults is a persistent dry cough. The cough often continues to worsen, eventually turning into a productive cough that brings up mucus. Children often have a fever or sluggishness before developing a cough that gets worse at night.


Most symptoms of walking pneumonia, including fever and body aches, start to go away within five days. However, the cough caused by foot pneumonia can last a month or more.

If you think you have walking pneumonia, you should see your healthcare provider, who may be able to prescribe an antibiotic to help you recover faster.


Fungal pneumonia is caused when fungi in the environment enter and begin to grow in the lungs. This most often occurs in people who have a weakened immune system or other chronic health problems.


The most common causes of fungal pneumonia are:

  • Pneumocystis pneumonia: This fungus can cause severe pneumonia. It most often affects people living with HIV / AIDS or those who have had an organ transplant.
  • Coccidioidomycosis: This fungus causes valley fever and is found in the southwestern United States.
  • Histoplasmosis: This fungus is found in bird and bat droppings in the Mississippi and Ohio valleys. People who are repeatedly exposed to histoplasmosis are at risk for pneumonia.
  • Cryptococcus: This fungus is common in all soils, but is only likely to cause pneumonia in people with weakened immune systems.


Fungal pneumonia is often serious, especially since the most susceptible people have other health problems. Antifungal drugs can help treat fungal pneumonia.

Aspiration and Chemistry

Aspiration pneumonia occurs when a person sucks or breaths a foreign substance into their lungs. This most often happens with food or drink. When a person swallows, a small amount of food or drink can go down the “wrong pipe” into the lungs rather than the stomach.

This can happen without a person realizing it, especially in the elderly, people with anesthesia, or those with other health conditions.


When a person takes in food or drink, bacteria can get into the lungs. This can lead to the development of bacterial pneumonia.

In other cases, a person can breathe chemicals that damage the lungs. This can lead to chemical pneumonia, an inflammation of the lungs that can progress to pneumonia. Common household chemicals like chlorine, fertilizers, and smoke can all cause chemical pneumonia, as can stomach acid inhaled into the lungs.


Treatment for aspiration or chemical pneumonia will depend on the substance you inhaled and its ability to be cleared from the lungs.


Chemical pneumonia can lead to chronic lung problems. If you think you have inhaled chemicals, it is best to see a doctor.

A word from Verywell

Pneumonia is a common health problem, but it can be very serious. It is a leading cause of hospitalization and death among American adults, with 1.3 million Americans diagnosed with pneumonia in a hospital each year.

Once you know the different types of pneumonia and their causes, there are steps you can take to reduce your risk of pneumonia. These should include:

  • Practice good hygiene, including frequent hand washing, to prevent the spread of infection
  • Quit smoking and reduce exposure to environmental toxins
  • Follow nutritional guidelines to help keep your immune system healthy

There is no way to fully protect yourself against pneumonia, but understanding the disease can better equip you to deal with it.