Pneumonia | Infectious Diseases | JAMA | JAMA Network
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JAMA Patient Page
February 9, 2016


JAMA. 2016;315(6):626. doi:10.1001/jama.2016.0320

Pneumonia is a lung infection that can be caused by bacteria, viruses, or fungi.

When you breathe in, oxygen-rich air travels into the body through the airways (trachea, bronchi, and bronchioles) in your lungs. At the ends of the airways, oxygen is exchanged for carbon dioxide, which travels out of the body when you breathe out. Alveoli are very small air sacs at the ends of the airway branches where this gas exchange occurs. Pneumonia causes alveoli to become inflamed and to fill up with fluid.

Bacteria are the most common cause of pneumonia in adults, while viruses are the most common cause in children younger than 5 years.


The symptoms of pneumonia range from mild to severe. Common symptoms include cough with phlegm (“wet cough”), difficulty breathing, fever, chest pain, fatigue, and confusion.

At-Risk Populations

While anyone can get pneumonia, certain groups are at higher risk of developing the disease. Children younger than 2 years and adults older than 65 years are at increased risk. Your risk is also higher if you

  • Have a weakened immune system

  • Have chronic lung disease, such as COPD, asthma, or cystic fibrosis

  • Have other chronic health problems, such as diabetes or heart disease

  • Smoke cigarettes


Vaccines can help prevent pneumonia. Pneumococcal vaccine helps protect you from a common cause of severe pneumonia. Getting the flu vaccine every year helps prevent pneumonia that is caused by the influenza virus or that occurs as a complication of having the flu. Pertussis, measles, varicella (chickenpox), and Hib vaccines help prevent less common causes of pneumonia.

Washing your hands with soap and water or using hand sanitizer regularly can help prevent the spread of germs that cause pneumonia. Quitting smoking increases your lungs’ ability to filter out germs and fight infections.

Diagnosis and Treatment

To diagnose pneumonia, your doctor will ask questions about your symptoms and your health history. Certain tests, including chest x-ray, blood tests, and sputum (phlegm) culture, may be performed to help make the diagnosis.

Treatment is based on what kind of germ is causing the infection and how severe your symptoms are. Bacterial pneumonia is treated with antibiotic medicines. Antibiotics will not help in cases of viral pneumonia, which often improves without treatment.

Pneumonia can be acquired in various settings. Causative germs and treatment may differ depending on whether you have community-acquired pneumonia (CAP), hospital-acquired pneumonia, or health care–associated pneumonia.

Many cases of pneumonia can be treated at home. If your symptoms are severe or you have other health problems, you may need to be treated in the hospital. A study in the February 9, 2016, issue of JAMA reports on antibiotic therapy in adults hospitalized with CAP.

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Article Information

Conflict of Interest Disclosures: The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Sources: Centers for Disease Control and Prevention; National Heart, Lung, and Blood Institute.

Topic: Pulmonary