Pneumonia is an infection of the lungs which affects millions of people globally each year. In the USA alone, about 4 million people develop pneumonia annually and 40,000 to 70,000 of them die. In 1997, pneumonia and influenza combined ranked as the sixth leading cause of death world-wide.

What is Pneumonia?
Pneumonia is a serious infection or inflammation of the lungs that can be caused by various types of microbes, including bacteria, viruses, fungi, and parasites. Bacteria are the most common cause of pneumonia in adults over 30 years of age and the bacteria Streptococcus pneumoniae is the most common cause of bacterial pneumonia. When someone catches pneumonia, the infection causes the lungs to become inflamed and the air sacs in the lungs fill with pus and other liquid. Oxygen has trouble reaching the blood. If there is too little oxygen in the blood, the body cells cannot work properly. When the body defences are weakened in some way, by illness, old age, malnutrition, smoking, asthma, general debility or impaired immunity, the bacteria can multiply and cause serious damage. The infection quickly spreads through the bloodstream and the whole body is invaded.

Symptoms
Pneumonia often develops after an upper respiratory tract infection (an infection of the nose and throat). When this happens, symptoms of pneumonia may occur two or three days after the start of a cold or sore throat.

The onset of bacterial pneumonia can vary from gradual to sudden. In the most severe cases, the patient may have a high temperature, shaking chills, chattering teeth, severe chest pain, and a cough that produces rust-coloured or greenish mucus.

The patient sweats profusely, and breathing and pulse rate increase rapidly. Lips and nailbeds may have a bluish colour due to a lack of oxygen in the blood.

Diagnosis and Treatment
Diagnosis is based on the characteristic symptoms combined with a chest x-ray. In the young and healthy, early treatment with the correct antibiotics can cure bacterial pneumonia. There is not yet a general treatment for viral pneumonia, although antiviral drugs are used for certain kinds.

The drugs used to fight pneumonia are determined by the germ causing the pneumonia and the judgement of the doctor. After a patient's temperature returns to normal, medication must be continued according to the doctor's instructions, otherwise the pneumonia may recur. Relapses can be far more serious than the first attack.

Besides antibiotics, patients are often prescribed supportive treatment: proper diet, bed-rest and oxygen to increase oxygen levels in the blood when needed. In some patients, medication to ease chest pain and to provide relief from violent cough may be necessary.