Types of Pneumonia According to the Illness-Causing Agent
One element that has to be taken into consideration is the main agent that causes the infection. According to Johns Hopkins Medicine, the main types of pneumonia include:2
• Bacterial pneumonia — It’s commonly caused by bacteria strains such as Streptococcus pneumoniae, Chlamydophila pneumonia or Legionella pneumophila. Bacterial pneumonia can affect people of all ages, leading to a weakened ability to exchange oxygen and carbon dioxide, as well as breathlessness and pain when you try to breathe in.3
Bacterial pneumonia can be mild or severe, depending on the strength of the bacteria strain4 and how long it takes from the time you acquire it until the disease is diagnosed and treated.
• Viral pneumonia — This disease is triggered by viruses such as influenza, chickenpox, adenoviruses or respiratory syncytial virus, and accounts for at least one-third of all pneumonia cases.5 A patient may develop viral pneumonia via coughing, sneezing or touching an object contaminated by an infected person.6 People who have viral pneumonia may be more susceptible to bacterial pneumonia.7
• Mycoplasma pneumonia — This pneumonia is caused by Mycoplasma pneumoniae, an “atypical bacterium” considered to be one of the smallest agents that affect humans.8,9 This type of pneumonia is also called atypical or walking pneumonia.10
Mycoplasma pneumonia affects people of all age groups,11 but it’s more common among those under 40 years old.12 This disease can spread from one person to another when one person comes into contact with fluids expelled by an infected person via coughing or sneezing.13 People who have this disease exhibit different symptoms and physical signs, but overall they have mild and widespread pneumonia14 (most cases tend to be mild15) or a dry cough.16
Take note, while in most instances Mycolplasma pneumonia is a mild disease, sometimes it can become very serious, depending on your overall health and any coinfections you may have.17 That is why it’s especially important to be diagnosed properly and treated right away if you have symptoms that make you suspicious that you may have pneumonia.
• Aspiration pneumonia — Infections or inhalation of food, vomit or saliva can lead to this type of pneumonia. This illness goes by other names, such as necrotizing pneumonia, anaerobic pneumonia, aspiration pneumonitis and aspiration of vomitus.18
Aspiration pneumonia can be difficult to treat on some occasions because, usually, people who acquire this disease are already sick to begin with, or are dealing with other debilitating conditions19,20
• Fungal pneumonia — Various endemic or opportunistic fungi are said to be the main causes of fungal pneumonia. Fungal pneumonia often develops after a patient inhales spores or conidia, or once the body “reactivates” a latent infection. You should note that fungal pneumonia cases are quite difficult to diagnose.21
The incidence of fungal pneumonia may be high in states located in the southwestern portion of the U.S. such as Arizona and California, in Mexico, and in other Central and South American countries.22
Types of Pneumonia According to Where the Infection Was Acquired
Pneumonias may also be classified according to the location where you were exposed to the agent responsible for your infection:23
• Community-acquired pneumonia (CAP) — CAP is essentially an infection caused by bacteria, viruses, fungi or parasites. Patients who have CAP acquire the disease outside of hospitals or other health care settings.24
A variety of factors contribute to CAP, but two commonly identified pathogens associated with CAP include Streptococcus pneumonia and Haemophilus influenzae. CAP can also be caused by influenza viruses, which can make the condition more serious, and even fatal in some instances for immunocompromised indivudals.25
Community-acquired pneumonia is one of the most common types of pneumonia,26 with the majority of cases occurring during winter.27 A 2006 article in the journal American Family Physician highlights that around 5.6 million cases of community-acquired pneumonia are reported annually in the U.S., and patients spend $8.4 billion a year to alleviate the disease.28
• Hospital-acquired pneumonia (HAP) — This type of pneumonia tends to develop in individuals after they’re admitted to a hospital for another illness. HAP tends to be more dangerous compared to community-acquired pneumonia because you’re already sick when you’re infected with HAP. Your risk for HAP also rises if you use a respirator to help with breathing. Plus, hospitals are usually hotbeds for antibiotic-resistant germs that may cause this disease.29,30
• Health care-associated pneumonia — This refers to an infection that affects a nonhospitalized patient. It’s often seen in other health care settings such as nursing homes and dialysis centers.31
Specific Types of Pneumonia You Should Watch Out For
There are other types of pneumonia that don’t fall under the categories listed above. Regardless, it’s still important to be vigilant and consult a physician or health expert when you notice symptoms of these infections, since some diseases might lead to further harm:
Pneumococcal pneumonia — This is mainly caused by a bacteria called Streptococcus pneumoniae. This disease is common among children below 2 years of age and adults 65 years old and above.
Pneumococcal pneumonia infects the upper respiratory tract and can spread to the nervous system, other parts of the lungs, ears or blood if not treated immediately.32
Bronchial pneumonia or bronchopneumonia — This type of pneumonia affects both the lungs and the bronchi.33,34
The Streptococcus pneumonia bacterium is the common culprit of this disease, but it can also be triggered by other strains such as Staphylococcus aureus, Haemophilus influenza or Klebsiella pneumoniae.35
Lobar pneumonia — Another disease caused by the Streptococcus pneumoniae bacteria strain, this is characterized by an infection in one lobe or area of the lung.36
Legionella pneumonia — Also known as Legionnaires’ disease, this is caused by the Legionella bacterium strain. Patients affected by Legionella pneumonia inhale the bacteria. Older adults, smokers and immunocompromised individuals are most prone to this disease.37
Bilateral pneumonia — This is caused by a bacterial, viral or fungal infection that affects both lungs. It’s also known as double pneumonia, and patients have difficulty breathing and show traces of fluids in the lungs.
The risk for being infected with this disease is high among older people who have difficulty swallowing, those taking immunosuppressing drugs and tobacco smokers.38
Eosinophilic pneumonia — Also known as acute eosinophilic pneumonia (AEP), this is a rare condition wherein eosinophils, a type of white blood cell that’s part of your immune system, greatly multiply and accumulate in your lungs.
Eosinophils form in order to combat allergens, inflammation or infection. The cause of the disease is yet to be determined, although researchers are investigating the potential impacts of environmental and lifestyle choices toward the development of this type of pneumonia.39
Lipoid pneumonia — Lipoid pneumonia is a rare disease wherein oily and fatty substances enter the lungs.40,41
According to the Journal of General Internal Medicine, lipoid pneumonia is often caused by inhalation or even ingestion of fatty substances such as petroleum jelly, mineral oils, nasal drops and olive oil.42
Hypostatic pneumonia — Common among inactive or immobile elderly and debilitated individuals, hypostatic pneumonia is a disease characterized by a patient’s lungs failing to expand properly because the patient is either inactive or immobile.43,44
Interstitial pneumonia — Considered to be rare, this happens when there’s an inflammation or thickening of the lungs’ interstitium caused by bacteria, fungi or viruses.
Since the interstitium’s main purpose is to deliver support to the alveoli (or air sacs) in your lungs, this disease may negatively impact proper function of the alveoli and potentially lead to lung tissue scarring, among other complications.45,46