 An unusual rise in the number of PCP cases in North America, noticed when physicians began requesting large quantities of the rarely used antibiotic pentamidine, was the first clue to the existence of AIDS in the early 1980s.Prior to the development of more effective treatments, PCP was a common and rapid cause of death in persons living with AIDS.Much of the incidence of PCP has been reduced by instituting a standard practice of using oral co-trimoxazole (Bactrim / Septra) to prevent the disease in people with CD4 counts less than 200/μL.