Formerly known as Pneumocystis carinii pneumonia (PCP). A lung infection caused by the fungus Pneumocystis jiroveci. Symptoms include a cough (often mild and dry), fever, and shortness of breath. The fungus is common in the environment and does not cause illness in healthy people. Pneumocystis jiroveci pneumonia occurs only in people with weakened immune systems. In people with HIV, Pneumocystis jiroveci pneumonia is an AIDS-defining condition.