[A very up-to-date stage in the fate of infectious diseases: parasitic and fungal opportunistic infections].

Opportunistic parasitosis and mycosis are becoming ever more widespread, mainly under the influence of major immunodeficiencies, either acquired (AIDS) or therapeutic. In this general overview, their main aspects, both clinical and epidemiological, are underlined. In terms of epidemiology, three types of phenomena have been observed: 1) emergence of human parasitosis unknown before (microsporidiosis due to Enterocytozoon bieneusi, Encephalitozoom hellem or Septata intestinalis); 2) among the human parasites already known, identification of very pathogenic strains (Toxoplasma gondii, Aspergillus fumigatus, Cryptococcus neoformans); 3) origin probably or certainly nosocomial of certain infections (pneumocystosis; toxoplasmosis and visceral leishmaniasis transmitted during bone-marrow or organ transplantations). The development of deep mycosis (invasive aspergillosis) is particularly promoted by granulopenia and alterations in the phagocytosis. On the other hand, opportunistic protozoosis (toxoplasmosis and leishmaniasis) and helminthiasis (strongyloidosis due to Strongyloides stercolaris) are related, above all, to disorders in cellular immunity (deficit of CD4+, mainly). Finally, several of these infections may be characterised by a variety of clinical pictures and outcome, depending on the contributory factors (immunodeficit or not) which led to the development of the infection.