Pneumonia: Types and Causes

Updated: October 13, 2017

Pneumonia  is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. The alveoli will be filled with fluid or pus, making it difficult to breathe. It can be caused by bacteria, viruses, or fungi. The most common type of pneumonia in adults is bacterial pneumonia.
Bacteria, viruses, or fungi can cause the infection. There are also a few noninfectious types of pneumonia that are caused by inhaling or aspirating foreign matter or toxic substances into the lungs. Pneumonia is more common in elderly people and often occurs when the immune system becomes weakened by a prior infection or another medical conditions.
Pneumonia is generally more serious when it affects older adults, infants and young children, those with chronic medical conditions, or those with weakened immune function.

Types of Pneumonia:

Pneumonia are classified by the cause of the infection, where the infection was transmitted, and how the infection was acquired.

Types by germ:

These are classified according to the organism that caused the infection.

Bacterial pneumonia:

Bacteria are the most common cause of community-acquired pneumonia (CAP) with streptococcus pneumoniae. Bacterial pneumonia can also be caused by chlamydophila pneumonia and legionella pneumophila can also cause .

Viral pneumonia:

Viral pneumonia occurs because of respiratory viruses , especially in young children and older people. Viral pneumonia is usually not serious and lasts for a shorter time than bacterial pneumonia.

Mycoplasma pneumonia:

Mycoplasma organisms are neither viruses nor bacteria, but they have traits common to both. Mycoplasmas generally cause mild cases of pneumonia, in older children and young adults.

Fungal pneumonia:

Fungal pneumonia is uncommon, but occurs more commonly in individuals with weakened immune systems due to AIDS, immunosuppressive drugs, or other chronic diseases . Fungi from soil or bird droppings can cause pneumonia in people who inhale large amounts of the organisms.
Pneumocystis jirovecii pneumonia (PCP) is a kind of fungal pneumonia in which generally people with weakened immune systems, such as those with AIDS are affected. In fact, PCP can be one of the first signs of infection with AIDS.

Types by location:

Pneumonia is also classified according to where it was acquired.

Hospital-acquired pneumonia (HAP):

This type of bacterial pneumonia is acquired during a hospital stay. It can be more serious than other types, because the bacteria involved may be more resistant to antibiotics. It develops in ill patients already hospitalized or under medical care for another condition. Being on a ventilator for respiratory support increases the risk of acquiring HAP. Health-care-associated pneumonia is acquired from other health-care settings, like kidney dialysis centers, outpatient clinics, or nursing homes.

Community-acquired pneumonia (CAP):

This refers to pneumonia that is acquired outside of a medical or institutional setting. It is more common than hospital-acquired pneumonia and occurs in winter.

Types by how they are acquired:

Pneumonia can also be classified according to how it is acquired.

Aspiration pneumonia:

When you inhale bacteria into your lungs from food, drink, or saliva, this type of pneumonia occurs. This type is more likely to occur if the swallowing reflex is impaired, such as with brain injury or in an intoxicated person.

Ventilator-associated pneumonia (VAP):

Pneumonia that arises from being on a ventilator for respiratory support in the intensive-care setting is known as ventilator-associated pneumonia.

Causes of Pneumonia:

Germs called bacteria, viruses or fungi usually cause pneumonia. Usually pneumonia starts when you breathe the germs into your lungs. Most often you get the disease after having a cold or the flu as these illnesses make it hard for your lungs to fight infection. So it is easier to get pneumonia. Having a long-term or chronic disease like asthma, heart disease, cancer, or diabetes also makes you more likely to get pneumonia.