Dear Colleagues:

Pneumocystis jirovecii is an atypical fungus that exhibits high pulmonary tropism and specificity for the human host. Recent studies have begun to change the post-AIDS epidemic misconception that Pneumocystis pneumonia (PcP) was an infrequent disease and show that PcP remains a major opportunistic infection among HIV-infected patients and an emerging problem in non-HIV immunocompromised patients worldwide. In developed countries, the increase in PcP corresponds mainly with non-HIV patients, not only among those with transplant or cancer but also in subjects with underlying chronic lung diseases suggesting that PcP infection remains a public health problem with emerging new players.

In developing countries, a limited number of epidemiological studies have evaluated PcP prevalence and described an increased rate of infections in Africa, Asia and South America.

Besides Pneumocystis infection, colonization has been demonstrated not only in HIV-infected and non-HIV-infected immunosuppressed adults, but also in patients with chronic lung diseases. These groups are likely to represent a major reservoir of infection and further underline the need for increased efforts towards a better characterization of emerging risk groups and areas to improve prophylactic strategies to reduce disease burden.

One of the main challenges of studying pneumocystis is the inability to culture the organism. In recent years due to the rapid development of molecular tools, much has been learned about the epidemiology and biology of this challenging pathogen. However, the pathogenesis of the infection and new treatment options remains tremendously challenging areas where further investigations are needed.

In this Research Topic, we aim to provide a comprehensive up-to-date account on the status of relevant research in the field and highlight the potential of new tools and approaches to solve some longstanding issues regarding this opportunistic pathogen.

This Research Topic welcomes contributions in the form of Original Research and Review that focus on, but are not limited to, the following issues:

• Epidemiology of PcP in developed and developing countries
• Molecular epidemiology and modes of transmission of Pneumocystis infection
• Genomics, transcriptomics and proteomics
• Host-pathogen interactions, pathogenicity, and immunology
• New findings related to drug discovery and treatment

Prof. Eva M. Carmona
Prof. F.J. Medrano
Guest Editors

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• Pneumocystis jirovecii
• Pneumocystis pneumonia
• epidemiology
• molecular biology
• immunology
• pathogenesis