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Pneumonia is a respiratory condition in which there is inflammation of the lung.

Community-acquired pneumonia refers to pneumonia in people who have not recently been in the hospital or another health care facility (nursing home, rehabilitation facility).

See also: Hospital-acquired pneumonia

Bronchopneumonia; Community-acquired pneumonia

Pneumonia is a common illness that affects millions of people each year in the United States. Germs called bacteria, viruses, and fungi may cause pneumonia.

Ways you can get pneumonia include:

• Bacteria and viruses living in your nose, sinuses, or mouth may spread to your lungs.
• You may breathe some of these germs directly into your lungs.
• You breathe in (inhale) food, liquids, vomit, or secretions from the mouth into your lungs (aspiration pneumonia)

Pneumonia caused by bacteria tends to be the most serious. In adults, bacteria are the most common cause of pneumonia.

• The most common pneumonia-causing germ in adults is Streptococcus pneumoniae (pneumococcus).
• Atypical pneumonia, often called walking pneumonia, is caused by bacteria such as Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae.
• Pneumocystis jiroveci pneumonia is sometimes seen in people whose immune system is impaired (due to AIDS or certain medications that suppress the immune system).
• Staphylococcus aureus, Moraxella catarrhalis, Streptococcus pyogenes, Neisseria meningitidis, Klebsiella pneumoniae, or Haemophilus influenzae are other bacteria that can cause pneumonia.
• Tuberculosis can cause pneumonia in some people, especially those with a weak immune system.

Viruses are also a common cause of pneumonia, especially in infants and young children.

See also: Respiratory syncytial virus

Risk factors (conditions that increase your chances of getting pneumonia) include:

• Cigarette smoking
• Recent viral respiratory infection (common cold, laryngitis, influenza)
• Difficulty swallowing (due to stroke, dementia, Parkinson's disease, or other neurological conditions)
• Chronic lung disease (COPD, bronchiectasis, cystic fibrosis)
• Cerebral palsy
• Other serious illnesses, such as heart disease, liver cirrhosis, or diabetes mellitus
• Living in a nursing facility
• Impaired consciousness (loss of brain function due to dementia, stroke, or other neurologic conditions)
• Recent surgery or trauma
• Immune system problem (See also: Pneumonia in immunocompromised host)

The most common symptoms of pneumonia are:

• Cough (with some pneumonias you may cough up greenish or yellow mucus, or even bloody mucus)
• Fever, which may be mild or high
• Shaking chills
• Shortness of breath (may only occur when you climb stairs)

• Sharp or stabbing chest pain that gets worse when you breathe deeply or cough
• Headache
• Excessive sweating and clammy skin
• Loss of appetite, low energy, and fatigue
• Confusion, especially in older people

If you have pneumonia, you may be working hard to breathe, or 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 health care provider will likely order a chest x-ray if pneumonia is suspected.

Some patients may need other tests, including:

• CBC to check white blood cell count
• Arterial blood gases to see if enough oxygen is getting into your blood from the lungs
• CT scan of the chest
• Gram's stain and culture of your sputum to look for the organism causing your symptoms
• Pleural fluid culture if there is fluid in the space surrounding the lungs

With treatment, most patients will improve within 2 weeks. Elderly or debilitated patients may need longer treatment.

Those who may be more likely to have complicated pneumonia include:

• Older adults or very young children
• People whose immune system does not work well
• People with other, serious medical problems such as diabetes or cirrhosis of the liver

Your doctor may want to make sure your chest x-ray becomes normal again after you take a course of antibiotics. However, it may take many weeks for your x-ray to clear up.

Possible complications include:

• Respiratory failure, which requires a breathing machine or ventilator
• Empyema or lung abscesses. These are infrequent, but serious, complications of pneumonia. They occur when pockets of pus form inside or around the lung. These may sometimes need to be drained with surgery.
• Sepsis, a condition in which there is uncontrolled swelling (inflammation) in the body, which may lead to organ failure
• Acute respiratory distress syndrome (ARDS), a severe form of respiratory failure

Call your doctor if you have:

• Worsening respiratory symptoms
• Shortness of breath, shaking chills, or persistent fevers
• Rapid or painful breathing
• A cough that brings up bloody or rust-colored mucus
• Chest pain that worsens when you cough or inhale
• Night sweats or unexplained weight loss
• Signs of pneumonia and weak immune system, as with HIV or chemotherapy

Infants with pneumonia may not have a cough. Call your doctor if your infant makes grunting noises or the area below the rib cage is retracting while breathing.

Wash your hands frequently, especially after blowing your nose, going to the bathroom, diapering, and before eating or preparing foods.

Don't smoke. Tobacco damages your lung's ability to ward off infection.

Vaccines may help prevent pneumonia in children, the elderly, and people with diabetes, asthma, emphysema, HIV, cancer, or other chronic conditions:

• Pneumococcal vaccine (Pneumovax, Prevnar) lowers your chances of getting pneumonia from Streptococcus pneumoniae.
• Flu vaccine prevents pneumonia and other problems caused by the influenza virus. It must be given yearly to protect against new virus strains.
• Hib vaccine prevents pneumonia in children from Haemophilus influenzae type b.
• A drug called Synagis (palivizumab) is given to some children younger than 24 months to prevent pneumonia caused by respiratory syncytial virus.

If you have cancer or HIV, talk to your doctor about additional ways to prevent pneumonia and other infections.

Higgins K, Singer M, Valappil T, Nambiar S, Lin D, Cox E. Overview of recent studies of community-acquired pneumonia. Clin Infect Dis. 2008;47:S150-156.

Centers for Disease Control and Prevention. Recommended Immunization Schedule for Ages 0 - 6 Years. United States, 2009.

Centers for Disease Control and Prevention. Recommended Immunization Schedule for Ages 7 - 18 Years. United States, 2009.

Centers for Disease Control and Prevention. Recommended Immunization Schedule for Adults. United States, 2009.

Li JZ, Winston LG, Moore DH, Bent S. Efficacy of short-course antibiotic regimens for community-acquired pneumonia: a meta-analysis. Am J Med. 2007;120:783-790.

Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007 Mar 1;44 Suppl 2:S27-72.