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	Pneumonia
	Definition
	Pneumonia is an inflammation of the working tissue in the lungs. White cells in the lungs occur in a pattern that prevents the alveoli, the air-exchanging part of the lungs, from performing properly. This condition is potentially life-threatening since you need this air exchange function to live.
	Cause
	This condition is caused by a wide variety of bacteria, viruses, fungi, and other types of organisms that evade the impressive range of defenses against them in the upper respiratory tract or enter through the mouth, evading the epiglottis. Infectious agents may enter through the mouth if you lose consciousness, have an inadequate cough, have a seizure or stroke, or undergo general anesthesia: These events can weaken or paralyze the reaction of the epiglottis and permit microbes into the windpipe, wending their way down into the lung during respiration. Smoking contributes to pneumonia since it damages the small hairs (cilia) that line the respiratory tract and sweep out invading germs. Malnutrition or conditions like kidney failure or sickle cell disease also impair the lung's ability to get rid of microorganisms that cause pneumonia. And viral infections of the upper respiratory tract can predispose a person to pneumonia because the viruses paralyze the protective cilia. Among children 12 and under, the most frequent cause of pneumonia is the pneumococcus bacterium. Among adolescents and young adults, the most frequent infective agent is a bacteria-like microbe called Mycoplasma pneumoniae. Bacterial pneumonia can also ensue as a complication of influenza A; secondary infections are most often caused by Streptococcus pneumoniae, Haemophilus influenzae, or (most serious of all) Staphylococcus aureus. A recently discovered form of pneumonia is Legionnaires' disease, caused by the Legionella pneumophila bacterium. This disease can occur sporadically or in epidemics as the first known one did, in 1976, at an American Legionnaires' convention in Philadelphia. The sporadic cases may be caused by exposure to an air-conditioning system or water tap carrying the bacteria. Legionnaires' disease is very common in certain cities such as Los Angeles and Pittsburgh and in some states such as Montana.
	Diagnosis
	To diagnose pneumonia, a physician first listens to a patient's chest, checking for fine, crackling noises, and characteristic dull thuds when it is tapped. A definitive diagnosis cannot be made, however, without chest x-rays, which show patches in the lung where air sacs are filled with fluid and debris instead of air. To determine the particular infective agent, lab tests can be done on sputum, urine, and blood samples, but these tests are not completely reliable. Most viral pneumonias are mild. Symptoms include fever, headache, malaise, chills, and cough. Bacterial pneumonia, which is more dangerous, usually causes attacks of shaking chills, high temperature (up to 105°F / 40.6°C), rapid breathing, and coughing, at first dry but then producing rust-colored sputum. Headache, nausea, and vomiting may also occur. The symptoms of bacterial pneumonia at first resemble those of a chest cold, with a dry cough and then a sputum-producing cough. When bacterial pneumonia occurs as a complication of influenza A, flu symptoms often disappear before the patient suddenly worsens with fever, cough, and shortness of breath. In the case of Legionnaires' disease, after an incubation period of 2 to 10 days, the patient develops fever, general muscular pain, chills, abdominal pain, diarrhea, nonproductive cough, sore throat, and sometimes headache and confusion. This disease can cause renal failure and may appear to be kidney disease. The diagnosis is made by testing the sputum or urine for particular antigens. A blood test is of little value since the disease must have progressed for some time before the blood tests positive. Pneumonia caused by bacteria that usually live in the mouth but have been aspirated into the lung (during unconsciousness for example) develops slowly and is difficult to diagnose. Initially, bacterial pneumonia causes people to lose their appetites, lose weight, and run a fever before they develop foul-smelling sputum.
	Treatment
	Fortunately, antibiotics are effective against bacterial pneumonia, but even after the infection has cleared, coughing can persist for several days or weeks. If a person is very ill, a test of arterial blood gases should be performed to ensure that he or she is getting adequate oxygen. Otherwise the person should be hospitalized in an intensive care unit and receive oxygen. The organisms that cause pneumonia do not directly cause death, but may dangerously limit oxygen intake with fatal consequences. When pneumonia is caused by Streptococcus pneumoniae, Haemophilus influenzae, or Staphylococcus aureus, antibiotics that kill all three organisms are usually prescribed to prevent further bacterial infection (Staphylococcus in particular is very dangerous). Legionnaires' disease progresses rapidly and requires hospitalization. The usual treatment is administration of the antibiotic erythromycin (or similar drugs that cause fewer side effects, such as clarithromycin or zithromycin) or rifampin. When pneumonia is caused by bacteria that usually live in the mouth but are aspirated into the lung, patients require hospitalization so that intravenous antibiotics can be given for 2 or 3 weeks. After release from the hospital, oral antibiotics should be continued for up to several months. In all cases, the treating doctor must know where the organism was contracted in order to prescribe the correct antibiotic. In each geographical area, there are strains of bacteria that have become resistant to certain antibiotics. For example, if someone takes a trip to Boston and comes back with a bacterial pneumonia due to H. influenzae, the doctor would be less likely to prescribe ampicillin because at the present time, 50 percent of such cases in Boston are resistant to ampicillin.
	Prevention
	Pneumonia caused by Pneumococcus by far the most prevalent type of bacterial pneumonia can now be prevented with a vaccine. The vaccine also protects against the 22 other most prevalent causes of bacterial pneumonia. (All together there are 83 pneumococci, but 23 of them cause the majority of illnesses.) People who should be vaccinated include: Anyone with chronic lung disease Anyone over the age of 60 Anyone who has had his or her spleen removed or damaged Anyone with sickle-cell anemia In addition, if cost is not a concern, it is now recommended that people receive the vaccine at age 50 since research indicates people develop more antibodies if they receive the vaccine earlier.
	Male/Female Differences
	Statistically, males get more pneumonia because of their heavier use of alcohol; alcohol lowers the body's resistance to infection, and people who abuse this drug are more prone to a number of infections than those who abstain. See also: 'Effects of Alcohol Abuse'