Pneumonia Pneumonia is a serious infection or inflammation of the lungs. There are two main types of pneumonia, one of them is bacterial pneumonia. This can attack anyone from newborns to the elderly. Alcoholics, debilitated people, post-operative patients, people with respiratory diseases or viral infections, and people who have weakened immune systems are at greater risk. Pneumonia bacteria are present in some healthy throats. When the body's defenses are weakened in some way, due to disease, old age, malnutrition, general weakness or weakened immune system, bacteria can multiply and cause serious damage. Usually, as a person's resistance decreases, bacteria enter the lungs and inflame the air sacs, and a person's temperature can rise as high as 105 degrees F. The other is viral pneumonia. Half of all pneumonias are believed to be caused by viruses. More and more viruses are being identified as causing respiratory infections, and while most attack the upper respiratory tract, some produce pneu...