Pneumonia is actually the major collection of symptoms of various other problems in the lungs, particularly bacterial or viral infections. Pneumonia is not just one disease, though "one of the most ancient known diseases," but may be caused by many "conditions" or "caustive organisms"; one of the major bacteriological causes is Streptococcus pneumoniae. Inflammation in the lungs is the major symptom, causing shortness of breath, fluid buildup, and coughing. Pneumonia is a very common side effect of other medical conditions, including auto-immune disorders, medical effects, and physical injury. Because of this, there is no single treatment, and the root cause must be properly diagnosed through medical tests before anything but the symptoms are treated. Because pneumonia is such a common side effect of other illnesses, it is still very common today, and it is a common cause of death around the world; most death from pneumonia occur in developing areas, where medical treatment is not as common, effective, or safe.
Pneumonia is caused by an infection of the lung. This is due to germs. There are different types of germs that may cause pneumonia. The most commonly known bacteria to cause it is Streptococcus pneumoniae (pneumococcus). Another one is called walking pneumonia and is normally developed more in elderly people. People who have poor immune systems can get pneumonia from the bacteria Pneumocystis jiroveci. Viruses can also cause pneumonia if untreated. An example is when someone gets the flu, does not get better nor seek treatment, and eventually the illness becomes pneumonia.