Pneumonia

What Is It?

Pneumonia is an infection of the lungs. Most pneumonias are caused by bacterial infections, and the most common cause in the United States is the bacteria Streptococcus pneumoniae. Other bacteria, such as Mycoplasma and Legionella, as well as certain viruses, also can cause pneumonia. However, because these less common infections do not always cause all of the classic pneumonia symptoms, they often are called atypical pneumonias. Atypical pneumonias most commonly occur in people under age 40.

Pneumonia that develops when someone is hospitalized for another illness tends to be more serious, because the organisms found in a hospital have become resistant to many antibiotics. Also, because you are hospitalized, you are apt to be weakened by your other illnesses and less able to fight off the infection.

A type of pneumonia called aspiration pneumonia develops when chemical irritants and bacteria from the mouth or stomach are inhaled into the lungs. It is more common in people who have had strokes and have difficulty controlling their swallowing reflexes or people who are unconscious as a result of alcohol or other drug overdoses.

Symptoms

Most pneumonias cause fever, cough with sputum (coughed-up mucus), shortness of breath and fatigue. In older patients, fatigue or confusion can be the only or most noticeable symptoms. In atypical and viral pneumonias, a dry cough without sputum is more common.

Diagnosis

Your doctor first will ask about your symptoms. During the physical exam, your doctor will check to see if you are breathing rapidly. He or she also will look for confusion and a purplish hue in your lips, fingernails or hands because these can indicate that you have low levels of oxygen in your blood. Using a stethoscope, your health-care provider can listen through your back for abnormal sounds from the lungs. The diagnosis of pneumonia most often is confirmed by an X-ray. If the chest X-ray does not show pneumonia, but your symptoms and physical exam suggest pneumonia, your doctor may make the diagnosis by looking at sputum (coughed-up mucus) under a microscope or checking if a blood test shows an elevation of infection-fighting white blood cells. Samples of your sputum or blood also can be sent to a laboratory to identify the specific cause of your pneumonia. Identifying the infectious organism can help your doctor to choose the best antibiotic to treat the infection. However, even when no organism can be identified, the pneumonia still can be treated successfully with antibiotics.

Expected Duration