The March edition of CDC’s EID Journal contains a Medscape (CME) Activity that outlines the somewhat surprising, and as-yet not adequately explained rise in Pneumocystis jirovecii pneumonia in England over the last decade (Increasing Pneumocystis Pneumonia, England, UK, 2000–2010).
Up until a little over 30 years ago, Pneumocystis Pneumonia (initially erroneously indentified as P. carinii pneumonia, or PCP) was an exceedingly rare diagnosis, despite the fact that early everyone carries the fungus in their lungs.
Medical Trivia: When the true fungal culprit was determined to be P. jirovecii rather than P. carinii there were calls to drop its old abbreviation (PCP), but its use was so well ingrained that it was decided to shift its meaning to PneumoCystis (jirovecii) Pneumonia (see 2002 EID Journal article A New Name for Pneumocystis from Humans and New Perspectives on the Host-Pathogen Relationship).
As an opportunistic infection, rarely seen in healthy people, PCP didn’t make many headlines until it became associated with the rise in HIV cases in the early 1980s. So prevalent were PCP infections among HIV positive individuals that it was often the first overt clinical sign of AIDs.
But even as more HIV positive cases receive prophylactic antifungal drugs, and the number of AIDs related PCP infections have decreased, the overall number of PCP infections in the UK rose steadily over the first decade of the 21st century.
Yesterday, the HPA released the following report:
A form of pneumonia that was relatively rare before the AIDS epidemic of the 1980s has been shown to be now of wider significance following an analysis of hospital admission data, and other laboratory and epidemiological data for England, carried out by HPA scientists.
The data analysis was prompted by anecdotal reports from clinicians that the infection, Pneumocystis jirovecii (previously known as P. carinii pneumonia, PCP), may be increasing among immuno-suppressed patients not known to be HIV-positive.
This has been confirmed following examination of several national databases (Hospital Episode Statistics, routine laboratory reporting, death registrations and HIV surveillance data). Laboratory-confirmed incidence of Pneumocystis jirovecii, for example, rose by an average 7% per year between 2000 and 2010 whereas rates among HIV-positive adults were decreasing. Transplant patients, those with a haematological malignancy and those with pre-existing lung disease were among those diagnosed with Pneumocystis jirovecii.
Confirmation of increased incidence of a treatable infection outside the previously-known risk groups warrants further investigation and a review of prevention strategies, the HPA study concludes.
1.Maini R, Henderson KI, Sheridan EA, Lamagni T, Nichols G, Delpech V, et al (March 2013). “Increasing Pneumocystis pneumonia, England, UK, 2000-2010”, Emerging Infectious Diseases 19(3).
2. "Study recommends changes to pneumonia prevention strategies", HPA press release 15 March 2013.
The exacerbation of PCP is classically linked to immunosuppression, and may be caused by HIV, potent immunosuppressant therapies often used with organ transplants, hematologic malignancies, renal failure & dialysis, and connective tissue/inflammatory disease.
But the authors of the EID article were unable to fully account for the dramatic increase in PCP cases from these causes alone. They did identify a potential new risk factor: preexisting lung disease.
From the study’s abstract:
Hospital admissions indicated increased P. jirovecii pneumonia diagnoses among patients not infected with HIV, particularly among those who had received a transplant or had a hematologic malignancy. A new risk was identified: preexisting lung disease. Infection rates among HIV-positive adults decreased. The results confirm that diagnoses of potentially preventable P. jirovecii pneumonia among persons outside the known risk group of persons with HIV infection have increased. This finding warrants further characterization of risk groups and a review of P. jirovecii pneumonia prevention strategies.
The authors also write that:
Another possible explanation for the increase in P. jirovecii pneumonia cases is increased transmission of the P. jirovecii organism between susceptible persons. Levels of exposure of susceptible persons to infectious persons might be increased as a result of changes in the delivery of health care. New, more transmissible strains could be emerging and leading to increased spread in the health care environment. Further investigation into the contribution of outbreaks—and, thus, increased person-to-person transmission—to the increase is warranted.
Regardless of the cause, the rise in cases is concerning, as PCP patients are often severely ill, may require ICU treatment, and according to the CDC.
In immunocompromised patients, the mortality rate ranges from 5% to 40% in those who receive treatment. The mortality rate approaches 100% without therapy.