Pneumocystis Carinii Pneumonia (PCP) is pneumonia in premature infants and immunocompromised children and adults caused by a fungus.

Pneumocystis carinii is a common microorganism that exists in rats, guinea pigs, monkeys, dogs, sheep, humans, and other animals. Most people are infected with Pneumocystis carinii during childhood and develop no symptoms. In North America, 65 to 100 percent of children have been infected with Pneumocystis carinii by the age of four. In people with adequately...