The prevention of P. carinii pneumonia

Cosiderable evidence supports the conention that Pneumocystis carinii is one of the most prevalent of all infectious agents in humans. More than 90% of healthy adults in most parts of the world have acquired its asymptomatically. The organism, of uncertain taxonomic status-perhaps protozoan, perhaps fungal (Figure 1)-is believed to remain dormant unless the host's immune system is seriously impaired, whereupon replication and pulmonary disease ensue. Unlike other opportunistic infections in the immunocompromised host-for which dissemination is the rule-P. carinii infection almost always remains confined to the lungs of the patient with severe congenital or acquired immunodeficiency has seved as a herald for serious underlying in Europe half a century ago, P. carinii resurged a decade ago in its contemporary role as a major threat to the survival of AIDS patients. In the United States today, P. carinii pneumonia is one of the major causes of death acquire PCP, and it is fatal if untreated. Yet P. carinii pneumonia is usually prventable once the high-risk host is identified.