Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic alveoli—associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes. Infectious agents include: bacteria, viruses, fungi, and parasites.
Some common symptoms of pneumonia are a high fever (usually over 104), chills, a drowning sensation, excessive coughing that produces mucus, rapid swallowing or breathing, nausea, vomiting, diarrhea and extreme fatigue. If these symptoms have been occurring for several days and do not get better with over-the-counter medications, then a diagnosis of pneumonia is possible.
Viral pneumonia caused by the influenza virus may be severe and sometimes fatal. The virus invades the lungs and multiplies; however, there are almost no physical signs of lung tissue becoming filled with fluid. This pneumonia is most serious in people who have pre-existing heart or lung disease and pregnant women.
The most common cause of bacterial pneumonia in adults is Streptococcus pneumoniae (pneumococcus), but there is a vaccine available for this form of pneumonia. Atypical pneumonia, often called walking pneumonia, is caused by bacteria such as Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae.
In 2009, 1.1 million people in the U.S. were hospitalized with pneumonia and more than 50,000 people died from the disease. Globally, pneumonia kills more than one and a half million children younger than 5 years of age each year. This is greater than the number of deaths from any other infectious disease, such as AIDS, malaria or tuberculosis.
In the U.S., the most common bacterial cause of pneumonia is Streptococcus pneumoniae (pneumococcus) and the most common viral causes are influenza, parainfluenza, and respiratory syncytial viruses. In children younger than 1 year of age, respiratory syncytial virus (RSV) is the most common cause of pneumonia.
Pneumonia can be serious if its not treated quickly, especially for those who have compromised immune systems, the very young or the very old. Walking pneumonia is the term used for pneumonia that isn't as serious and allows you to "walk around" with it. Because walking pneumonia often feels like a cold or the flu, many people don't even know they have it.
When you get pneumonia from contact with germs you encounter in the course of your normal routine, it's called community-acquired pneumonia. These commonplace germs generally cause mild forms of pneumonia that doctors can treat without difficulty.
Severe, difficult-to-treat bacterial pneumonia is a major problem in health care facilities — not only hospitals and nursing homes, but also kidney dialysis centers and outpatient infusion centers, where people regularly receive cancer chemotherapy and other intravenous medications.
Children usually start to feel better in 1 to 2 days. For adults, it usually takes 2 to 3 days. Anyone who has worsening symptoms should see a doctor. People who have severe symptoms or underlying health problems may need treatment in a hospital. It may take 3 weeks or more before they can go back to their normal routines.
CAP is the most common type of pneumonia. Most cases occur during the winter. About 4 million people get this form of pneumonia each year. About 1 out of every 5 people who has CAP needs to be treated in a hospital.