What causes pneumonia

The lungs are sponge- like organs surrounded by a moist membrane called pleura. In the inhalation process the air is carried through the trachea (windpipe) into the lungs in 2 major airways, the bronchi. The bronchi subdivide almost 20 times into million smaller bronchioles which lead in the end to alveoli, clusters of tiny sacs, inside the lungs.

The lungs are usually protected against viruses and bacteria by the defense system of the organism, in every stage of the breathing process. The bacteria are prevented from entering the lungs and causing problems because the human organism is always exposed to them. In some cases however, the bacteria breach through the defense mechanism and reach the lungs. The reasons for this process are not well known.

Many types of pneumonia are characterized by difficult breathing which is cause by the inflammation and filling with fluids accumulation into the air sacs of the lungs (alveoli). This process is caused by the accumulating leukocytes – white cells which are a key part of the immune system and attack the invading organisms, the pathogen agents and the immune proteins.

Where to look for pneumonia

Where or how a person is exposed to pneumonia is sometimes a criterion for the classification of the disease.

• Pneumonia acquired in the community. A person can acquire the pneumonia in the course of his or her daily life: in school, at work, etc. This form of pneumonia resembles to a very rare but severe and often deadly form called acute eosinophilic pneumonia, which was encountered in soldiers that served in or near Iraq . This kind of resemblance may lead to delayed proper treatment due to misdiagnosis.
• Aspiration pneumonia is a form that appears when a person aspires (inhales) foreign matter into the lungs. Most cases are caused by the contents of the stomach reaches the lungs after vomiting. This process is caused by any affection of the normal gag reflex caused by brain injury or any other disorder.
• Opportunistic organisms can also cause pneumonia. This is a form of the condition that affects people with impaired immune system. The persons with AIDS, sickle cell disease and other conditions that impair the immune system are also affected by organisms that are harmless for an otherwise healthy person. Corticosteroids, chemotherapy or other medications that suppress the immune system can put a person at risk for contacting opportunistic pneumonia. P. carinii pneumonia is one form of the condition that only affects persons with compromised immune system.
• Nosocomial pneumonia is the form of pneumonia acquired in the hospital. This form can be acquired in the hospital, where the risk is higher, if the person is connected to a mechanical ventilator, is in the intensive care unit or has an impaired immune system. This form can be very severe and even deadly for young children, old people, people suffering from HIV/AIDS and chronic obstructive pulmonary conditions.