Epidemiology and management of invasive fungal infections in immunocompromised hosts

Fungal infections in man usually are divided into three categories based upon their major pathophysiological characteristics: superficial and cutaneous, subcutaneous and, systemic infections. The last category consists of two separate entities. First there are the so called "endemic mycoses" caused by dimorphic fungi including Coccidioides immiiis, Paracoccidioides brasiliensis, Histoplasma capsula tum and Blastomyces dermatitidis which occur in patients who live in, or have travelled through geographical regions in which these pathogenic fungi have their habitat. Although the consequences of endemic mycoses are sometimes very severe, these infections were not viewed as a very major subject in the field of infectious diseases, probably due to their relatively rare and geographically restricted occurrence. The second entity consists of opportunistic infections caused by fungi that are ubiquitously present around the globe. The number of these infections has increased dramatically during the last three decades. For example, in 1966 invasive aspergillosis was called a disease of medical progress, and world literature on this subject was reviewed in a paper only six pages in length. In contrast in 1990, Denning et al. used 55 pages only to review the literature on the treatment of such infections. Several factors have been recognized to be responsible for this rapid increase, all of which are the consequence of advances in medicine. The use of antibacterial agents, the use of cytotoxic chemotherapy, organ transplantation combined with the use of immunosuppressive therapy, the use of indwelling catheters all one way or the other, compromise the defence mechanisms of the human host (Table 1 ) Some of these factors disrupt more than one line of defence; for example, longterm use of steroids, influences cellular immunity, macrophage function and neutrophil function, whereas the integrity of the skin and mucous membranes is little affected.

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