Types of Pneumonia

Pneumonia can be caused by bacterial, viral, or fungal infections

Table of Contents
View All
Table of Contents

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

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 from a fungal infection.

However, healthcare providers aren’t always able to identify a cause for pneumonia: one study found that in up to 62% of pneumonia cases no pathogen like a virus, bacteria, or fungus is identified.

When people discuss types of pneumonia, they also consider how severe the infection is. For example, walking pneumonia is a nonmedical term that’s used to refer to a mild case of pneumonia, where the patient can still be up and walking around. People also distinguish pneumonia cases by where they were picked up: for example, hospital-acquired pneumonia or community-acquired pneumonia.

A healthcare provider using a stehoscope on a seated man

Phynart Studio / Getty Images


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 airway can cause inflammation in the lungs and lead to pneumonia.


The most common viruses associated with viral pneumonia are:

If you have one of these viral infections, you won’t develop pneumonia in most cases. However, if you begin experiencing symptoms of pneumonia, like shortness of breath or a gray or blue tinge to the skin, you should contact your healthcare provider. 


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

If you have viral pneumonia you should get plenty of sleep and fluids. Antibiotics will not work against viral pneumonia, although in some cases your healthcare provider may prescribe an antiviral medication like Tamiflu (oseltamivir), Relenza (zanamivir), or Rapivab (peramivir).

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


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


The 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 grows in man-made water systems including hot tubs, plumbing systems, and cooling towers. It leads to a serious type of pneumonia known as Legionnnaire’s 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 walking pneumonia.
  • Chlamydia pneumoniae: This type of bacteria usually causes mild pneumonia, most often in people more than 40 years old.
  • Haemophilus influenzae: This type of bacteria is more likely to cause pneumonia in people with existing lung conditions, like 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 medication as prescribed, and let your healthcare provider know if your symptoms change.


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


Walking pneumonia is a type of bacterial infection also known as mycoplasma pneumonia. This type of pneumonia is mild, and you can usually continue your daily activities when you have it, hence the name walking pneumonia. Walking pneumonia is often spread in crowded living spaces, like dormitories or jails.


The most common symptom of walking pneumonia in adults is a persistent, dry cough. The cough often continues to get worse, eventually becoming a productive cough that brings up mucus. Kids often present with a fever or sluggishness before developing a cough that gets worse at night. 


Most of the symptoms of walking pneumonia, including fever and body aches, begin to resolve within five days. However, the cough from walking pneumonia can last for a month or more.

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


Fungal pneumonia is caused when fungi that are present in the environment enter and begin growing in the lungs. This happens most commonly in people who have a suppressed immune system or other chronic health conditions.


The most common causes of fungal pneumonia are:

  • Pneumocystis pneumonia: This fungus can cause severe pneumonia. It most commonly affects people 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 feces in the Mississippi and Ohio River Valleys. People who are repeatedly exposed to histoplasmosis are at risk for pneumonia.
  • Cryptococcus: This fungus is common in all soil, but is only likely to cause pneumonia in people with weakened immune systems. 


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

Aspiration and Chemical 

Aspiration pneumonia happens when a person aspirates, or breaths a foreign substance into their lungs. This happens most often 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 noticing, particularly in the elderly, people under anesthesia, or those with other health conditions. 


When a person aspirates food or drink, bacteria can be introduced into the lungs. This can lead to the development of bacterial pneumonia. 

In other cases, a person might breath in chemicals that damage the lungs. This can lead to chemical pneumonitis, an inflammation of the lungs that can progress into pneumonia. Common household chemicals like chlorine, fertilizer, and smoke can all cause chemical pneumonitis, as can stomach acid that is breathed into the lungs.


The treatment for aspiration or chemical pneumonia will depend on what substance you inhaled, and whether it is able to be removed from the lungs. 


Chemical pneumonitis can lead to chronic lung problems. If you believe you have inhaled chemicals, it's best to seek medical treatment.

A Word From Verywell

Pneumonia is a common health condition, but one that can be very serious. It is a leading cause of hospitalization and death among U.S. adults, with 1.3 million Americans diagnosed with pneumonia in a hospital each year.

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

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

There’s no way to entirely protect yourself against pneumonia, but understanding the condition can better equip you to face it. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Pneumonia.

  2. Centers for Disease Control and Prevention. New CDC study highlights burden of pneumonia hospitalizations among US adults.

  3. American Lung Association. What is walking pneumonia?

  4. American Lung Association. How is pneumonia treated?

  5. MedlinePlus. Chemical pneumonitis.

  6. Centers for Disease Control and Prevention. Pneumonia.

By Kelly Burch
Kelly Burch is has written about health topics for more than a decade. Her writing has appeared in The Washington Post, The Chicago Tribune, and more.