Until 1936, pneumonia was the No.1 cause of death in the U.S. Then the use of antibiotics brought it under control. Pneumonia and influenza combined have ranked as the sixth leading cause of death since 1979.

Pneumonia affects your lungs in two ways. Lobar pneumonia affects a section (lobe) of a lung. Bronchial pneumonia (or bronchopneumonia) affects patches throughout both lungs.

Pneumonia bacteria are present in some healthy throats. When body defenses are weakened in some way, by illness, old age, malnutrition, general debility or impaired immunity, the bacteria can multiply and cause serious damage. Usually, when a person's resistance is lowered, bacteria work their way into the lungs and inflame the air sacs.

When the air sacs become inflamed, the tissues in the lung becomes completely filled with liquid (this is called "consolidation"). The infection quickly spreads through the bloodstream and the whole body is invaded.

The pneumococcus is the most common cause of bacterial pneumonia. It is one form of pneumonia for which a vaccine is available, often referred to as the "Pneumonia shot".

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

Symptoms: The initial symptoms of viral pneumonia are the same as influenza symptoms: fever, a dry cough, headache, muscle pain, and weakness. Within 12 to 36 hours, there is increasing shortness of breath; the cough becomes worse and produces a small amount of mucus. There is a high fever and there may be blueness of the lips.

In the young and healthy, early treatment with antibiotics can cure bacterial pneumonia. There is no clearly effective treatment yet for viral pneumonia, which usually heals on its own.

The germ causing the pneumonia and the judgment of the doctor determines the drugs used to fight pneumonia. (Your doctor will probably request a sputum sample, this is a small amount of the mucous you are coughing up out of your lungs, to be sent to the laboratory so that it can be cultured to find out which antibiotic works best against the germ you have contracted.) 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 given supportive treatment: proper diet and oxygen to increase oxygen in the blood when needed. In some patients, medication to ease chest pain and to provide relief from violent cough may be necessary.

The vigorous young person may lead a normal life within a week of recovery from pneumonia. For the middle-aged, however, weeks may elapse before they regain their accustomed strength, vigor, and feeling of well- being.

Vaccine is also available to help fight pneumococcal pneumonia, one type of bacterial pneumonia. Your doctor can help you decide if you, or a member of your family, needs the vaccine against pneumococcal pneumonia. It is usually given only to people at high risk of getting the disease and its life-threatening complications.

The greatest risk of pneumococcal pneumonia is usually among people who:

• Have chronic illnesses such as lung disease, heart disease, kidney disorders, or diabetes.

• Are recovering from severe illness

• Are in nursing homes or other chronic care facilities

• Are age 65 or older

If you are at risk, ask your doctor for the vaccine.

The vaccine is generally given only once. It lasts for several years, but sometimes a booster shot is recommended. Ask your doctor.

Follow your doctor's advice. In serious cases, your doctor may advise a hospital stay. Or recovery at home may be possible.

Continue to take the medicine your doctor prescribes until it is finished or you are told that you may stop. This will help prevent recurrence of pneumonia and relapse.