Pneumonia is a lung infection caused by bacteria, virus, or fungus. The most direct endogenous sources of any of these microorganisms include infected nasal carriers, sinusitis, oropharynx, gastric, or tracheal colonization, and hematogenous spread (Alcon Fabregas & Torres, 2005). Although much is known about pneumonia, it remains the leading infectious cause of hospitalization and death in the United States ("Pneumonia," n.d.). One of the reasons why pneumonia is common is that the lungs are exposed to some ten thousand liters of air each day, as well as small amounts of saliva and even occasionally aspirated regurgitation, all of which can contain bacteria, viral and fungal agents, and other pathogens ("Pneumonia," n.d.).

Although pneumonia is contagious via airborne particles shared by infected persons, self-infection is far more common. This is why oral hygiene, nutrition, and other lifestyle issues are central to reducing disease prevalence. When the immune system has been compromised...
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