Types of Pneumonia

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

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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, doctors 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.

woman sick on her couch

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Viral

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.

Causes

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 doctor. 

Treatment

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 doctor 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

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. 

Causes

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).

Treatment

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 doctor know if your symptoms change.

Complications

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

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.

Symptoms

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. 

Treatment

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 doctor, who may be able to prescribe an antibiotic to help you recover more quickly. 

Fungal 

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.

Causes

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. 

Treatment

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. 

Causes

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.

Treatment

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. 

Complications

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. 

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Article Sources
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  1. MedlinePlus. Pneumonia. Updated January 4, 2021.

  2. Centers for Disease Control and Prevention. New CDC study highlights burden of pneumonia hospitalizations among US adults. Updated July 14, 2015.

  3. American Lung Association. What is walking pneumonia? Updated February 22, 2017.

  4. American Lung Association. How is pneumonia treated? Updated October 23, 2020.

  5. MedlinePlus. Chemical pneumonitis. Updated April 2, 2021. 

  6. Centers for Disease Control and Prevention. Pneumonia. Updated October 28, 2020.