Definition

     Pneumonia is an inflammation of the lungs caused by an infection. Many different organisms can cause it, including bacteria, viruses, and fungi.

Causes

     The list of organisms which can cause pneumonia is very large, and includes nearly every class of infecting organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

• Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus).

• Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus).

• Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae (the cause of what is often referred to as "walking" pneumonia).

• Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems (such as patients being treated for cancer with chemotherapy, or patients with AIDS. Classically considered a parasite, it appears to be more related to fungi.

• People who have reason to come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.

• A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's disease." The organism was traced to air conditioning units in the convention's hotel.

Symptoms

     The main symptoms of pneumonia are:

• Cough with greenish or yellow mucus; bloody sputum happens on occasion

• Fever with shaking chills

• Sharp or stabbing chest pain worsened by deep breathing or coughing

• Rapid, shallow breathing 

• Shortness of breath

     Additional symptoms include:

• Headache

• Excessive sweating and clammy skin

• Loss of appetite

• Excessive fatigue 

• Confusion  in older people

Screening and Diagnostics

     If you have pneumonia, you may be working hard to breathe, or may be breathing fast. Crackles are heard when listening to your chest with a stethoscope. Other abnormal breathing sounds may also be heard through the stethoscope or via percussion (tapping on your chest wall).

     The following tests may show signs of pneumonia:

• Chest x-ray

• Gram's stain and culture of your sputum to look for the organism causing your symptoms

• CBC to check white blood cell count; if high, this suggests bacterial infection

• Arterial blood gases to check how well you are oxygenating your blood

• CAT scan of the chest

• Pleural fluid culture if there is fluid in the space surrounding the lungs

Treatment

     If the cause is bacterial, the goal is to cure the infection with antibiotics. If the cause is viral, antibiotics will NOT be effective. In some cases it is difficult to distinguish between viral and bacterial pneumonia, so antibiotics may be prescribed.

      Many people can be treated at home with antibiotics. If you have an underlying chronic disease, severe symptoms, or low oxygen levels, you will likely require hospitalization for intravenous antibiotics and oxygen therapy. Infants and the elderly are more commonly admitted for treatment of pneumonia.

     You can take these steps at home:

• Drink plenty of fluids to help loosen secretions and bring up phlegm.

• Get lots of rest. Have someone else do household chores.

• Control your fever with aspirin or acetaminophen. DO NOT give aspirin to children.

     When in the hospital, respiratory treatments to remove secretions may be necessary. Occasionally, steroid medications may be used to reduce wheezing if there is an underlying lung disease.

Prevention

     Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia for certain patients. This is particularly true of the elderly and people with chronic diseases (such as asthma, cystic fibrosis, other lung or heart diseases, sickle cell disease, diabetes, kidney disease, and forms of cancer).

     A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to patients with chronic illnesses.

     Patients who have decreased immune resistance are at higher risk for infection with Pneumocystis carinii. They are frequently put on a regular drug regimen of trimethoprim sulfa and/or inhaled pentamidine to avoid pneumocystis pneumonia.