Pneumonia is a lung infection that can cause symptoms such as fever, chills, and a cough that produces green or yellow phlegm. This condition is often caused by bacteria (such as Streptococcus pneumoniae) or viruses. Most people can be treated at home with rest, fluids, and possibly antibiotics, but people with more severe symptoms may need treatment in the hospital.
What Is Pneumonia?Pneumonia is an infection within one or both lungs. It can be caused by a number of germs, including bacteria, viruses, or, in rare cases, fungi or parasites.
Pneumonia is a common infection. It is more common in men than women and in smokers compared to non-smokers. It is also potentially serious and even life-threatening.
Pneumonia TypesHealthcare providers separate pneumonia into different types based on where the infection occurred or on the germ that caused it.
Some different types include:
- Community-acquired pneumonia
- Hospital-acquired pneumonia
- Healthcare-associated pneumonia.
(Click Types of Pneumonia for more information.)
What Causes It?Each of the different types of pneumonia can be caused by a number of possible viruses, bacteria, fungi, or parasites. Viruses are thought to cause more infections than bacteria. Viral pneumonia is more common in children than in adults. Up to 30 percent of cases in adults are caused by viruses. Up to 35 percent of all cases of pneumonia in children are thought to be from viruses (see Pneumonia in Children).
Overall, the most common cause of pneumonia is the bacterium Streptococcus pneumoniae, also known as just pneumococcus.
In people with normal, functioning immune systems, fungal pneumonia is rather uncommon.
(Click Causes of Pneumonia for more information on the specific bacteria and viruses that most often cause pneumonia.)