Current Epidemiology of Pneumocystis Pneumonia

Alison Morris; Jens D. Lundgren; Henry Masur; Peter D. Walzer; Debra L. Hanson; Toni Frederick; Laurence Huang; Charles B. Beard; Jonathan E. Kaplan

Disclosures

Emerging Infectious Diseases. 2004;10(10) 

In This Article

PCP in Adults in Africa

In contrast to the situation in many other developing regions, PCP has been thought to be rare in African adults. Several representative series are summarized in Table 1 . Most early studies reported prevalence rates of 0% to 11% in HIV-infected patients,[30,31,33,34] although one early study found a rate of 33%.[35]

PCP might not have been commonly reported in Africa for several reasons. Limited resources for diagnosis may have led to lower estimates of PCP. Experienced laboratory personnel are required to prepare and interpret diagnostic specimens. Bronchoscopy is expensive, and induced sputum also requires specialized equipment and personnel to obtain adequate samples. Limited resources make empiric therapy of HIV-infected persons with pneumonia common, possibly leading to inaccurate estimates of the true incidence of PCP. HIV-infected African adults also have high rates of bacterial pneumonia and tuberculosis, diseases that may result in death at higher CD4+ cell counts and prevent many HIV-infected patients from reaching a stage at which they would be susceptible to PCP. Environmental factors, such as seasonal variations, might contribute to a low rate of PCP in Africa. However, high rates of anti-Pneumocystis antibodies among African children suggest that exposure to the organism is common.[19] Regional strains may be less virulent, or the population may be more resistant, as HIV-infected African Americans have been shown to have lower PCP rates compared to white Americans.[10] Detailed molecular study of the organism in different parts of the world is needed to resolve these issues.

The incidence of PCP in Africa may be growing as the AIDS epidemic progresses. A recent review concluded that cases of PCP seem to have increased over time,[23] but whether this increase resulted from actual changes in PCP incidence or from improved detection techniques is unclear. Some studies have reported higher rates of PCP in Africa compared to past findings ( Table 1 ). Malin et al. studied a group of 64 hospitalized HIV-infected patients in Zimbabwe in 1995.[35] These patients had pneumonia unresponsive to penicillin, and sputum samples were smear-negative for acid-fast bacilli (AFB). All patients underwent bronchoscopy with bronchoalveolar lavage (BAL). Twenty-one (33%) of these patients had PCP. Reasons for a higher rate of PCP among these patients included use of definitive diagnosis and probable selection bias by including only patients with severe pneumonia when other diagnoses, such as tuberculosis, had been excluded. Another study examined 83 patients hospitalized with respiratory symptoms.[36] All patients had sputum cultures that were negative for AFB and underwent bronchoscopy with BAL for diagnosis. Thirty-two patients (38.6%) were diagnosed with PCP. Not all studies have found high rates of PCP. Aderaye et al. reported that of 119 outpatients with respiratory symptoms and negative AFB cultures, only 11% had PCP.[32] Similarly, another recent study found PCP in 11% of patients who underwent autopsy after dying as an inpatient with respiratory symptoms.[31] Future research will be needed to clarify the risk for PCP in Africa.

In contrast to adults, HIV-infected children in Africa have high rates of PCP. Autopsy series describe rates of PCP from 14% to 51.3%, depending on the age group studied ( Table 2 ). Ikeogu et al. found that in Zimbabwe, 19 (15.5%) of 122 HIV-infected children who died <5 years of age had evidence of PCP at autopsy.[40] All cases except one were in infants <6 months. Another autopsy study from the early 1990s found that PCP was present in 11 (31%) of 36 HIV-infected infants but was not found in 42 HIV-infected children >15 months.[41] The largest autopsy series examined 180 HIV-infected children in Zambia.[38] Twenty-nine percent of the children died of PCP, making PCP the third leading cause of death overall. Among children <6 months of age, PCP was the most common cause of pneumonia, detected in 51.3%. Six of 84 HIV-negative children had evidence of PCP at autopsy. The most recent autopsy series reported that 10 (28.6%) of 35 HIV-infected children had PCP.[37]

Because autopsy studies examine terminal disease, their assessment of disease prevalence might be biased. Several authors described prevalence of PCP among children in clinic or hospital settings to estimate disease frequency more accurately. Most studies reported rates higher than those in adults. Two authors found rates >40% among HIV-infected children hospitalized with pneumonia.[42,43] Ruffini studied children from 2 to 24 months of age with pneumonia and found that 48.6% had PCP.[43] Madhi found that in 231 episodes of pneumonia in HIV-infected children, 101 (43.7%) were due to PCP.[39] PCP was most common in infants <6 months, although 35.7% of pneumonias in older children were also caused by PCP. Graham, in a smaller study of 16 cases of PCP in 93 children with HIV infection, also found that most cases of PCP occurred in infants.[42] The study reporting the lowest frequency of PCP among children with pneumonia found 15 (9.9%) of 151 HIV-infected children to have PCP.[44] Four non-HIV-infected children also had PCP. The authors speculated that the lower rate of PCP in their study may have been attributable to their inability to follow negative sputum examinations with bronchoscopy.

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