Current epidemiology<unk>  jirovecii The disease<unk>  is relatively rare in people with normal immune systems, but common among people with weakened immune systems, such as premature or severely malnourished children, the elderly, and especially persons living with HIV/AIDS (in whom it is most commonly observed).<unk>  can also develop in patients who are taking immunosuppressive medications. It can occur in patients who have undergone solid organ transplantation or bone marrow transplantation and after surgery. Infections with<unk>  are also common in infants with hyper IgM syndrome, an X-linked or autosomal recessive trait. The causative organism of<unk>  is distributed worldwide and<unk>  has been described in all continents except Antarctica. More than 75% of children are seropositive by the age of four, which suggests a high background exposure to the organism. A post mortem study conducted in Chile of 96 persons who died of unrelated causes (suicide, traffic accidents, and so forth) found that 65 (68%) of them had<unk>  in their lungs, which suggests that asymptomatic<unk>  infection is extremely common. Up to 20% of adults may be asymptomatic carriers at any given time, and asymptomatic infection may persist for months before being cleared by an immune response. P. jirovecii is commonly believed to be a commensal organism (dependent upon its human host for survival). The possibility of person-to-person transmission has recently gained credence, with supporting evidence coming from many different genotyping studies of P. jirovecii isolates from human lung tissue. For example, in one outbreak of 12 cases among transplant patients in Leiden, it was suggested as likely, but not proven, that human-to-human spread may have occurred.<unk>  and AIDS Since the start of the AIDS epidemic,<unk>  has been closely associated with AIDS. Because it only occurs in an immunocompromised host, it may be the first clue to a new AIDS diagnosis if the patient has no other reason to be immunocompromised (e.g. taking immunosuppressive drugs for organ transplant). An unusual rise in the number of<unk>  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,<unk>  was a common and rapid cause of death in persons living with AIDS. Much of the incidence of<unk>  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. In populations who do not have access to preventive treatment,<unk>  continues to be a major cause of death in AIDS.
Pneumocystis pneumonia
Pneumonia alba
Tuberculosis
Allergic bronchopulmonary aspergillosis
Histoplasmosis
Fungal pneumonia
Aspergillosis
Primary pulmonary coccidioidomycosis