Scanning electron micrograph (SEM) of a number of Gram-positive Streptococcus pneumoniae bacteria.

Pneumonia is an infection of the lungs that is usually caused by bacteria or viruses. Globally, pneumonia causes more deaths than any other infectious disease. However, it can often be prevented with vaccines and can usually be treated with antibiotics or antiviral drugs.

Click here to visit the CDC website for more information on Pneumonia.