Measles is highly contagious, but endemic transmission has been interrupted in the United States as a result of widespread vaccination; indigenous or imported cases have occasionally resulted in epidemics in the United States in unimmunized or partially immunized American or…
Antiviral chemotherapy typically requires a delicate balance between targeting critical steps in viral replication without interfering with host cellular function. Because viruses require cellular functions to complete replication, many antiviral agents exert significant host cellular toxicity, a limitation that has…
Pneumocystis jirovecii pneumonia (interstitial plasma cell pneumonitis) in an immunocompromised person is a life-threatening infection. Primary infection in the immunocompetent person is usually subclinical and goes unrecognized. The disease most likely results from new or repeat acquisition of the organism…
Etiology Mucormycosis refers to a group of opportunistic fungal infections caused by fungi of the order Mucorales, which are primitive, fast-growing fungi that are largely saprophytic and ubiquitous. These organisms are found commonly in soil, in decaying plant and animal…
Etiology Sporotrichosis is a rare fungal infection that occurs worldwide both sporadically and in outbreaks. The etiologic agent, Sporothrix schenckii, exhibits temperature dimorphism, existing as a mold at environmental temperatures (25-30°C [77-86°F]) and as a yeast in vivo (37°C [98.6°F]).…
Etiology Paracoccidioidomycosis (South American or Brazilian blastomycosis, Lutz-Splendore-Almeida disease) is the most common systemic mycosis in Latin America. It is a fungal infection that is endemic in South America, with cases reported in Central America and Mexico. Brazil accounts for…
Etiology Coccidioidomycosis (valley fever, San Joaquin fever, desert rheumatism, coccidioidal granuloma) is caused by Coccidioides spp., a soil-dwelling dimorphic fungus. Coccidioides spp. grow in the environment as spore-bearing (arthroconidia-bearing) mycelial forms. In their parasitic form, they appear as unique, endosporulating…
Etiology Blastomyces dermatitidis and Blastomyces gilchristii belong to a group of fungi that exhibit thermal dimorphism. In the soil (22-25°C [71.6-77°F]), these fungi grow as mold and produce spores, which are the infectious particles. Following soil disruption, aerosolized mycelial fragments…
Etiology Histoplasmosis is caused by Histoplasma capsulatum, a dimorphic fungus found in the environment as a saprobe in the mycelial (mold) form and in tissues in the parasitic form as yeast. Epidemiology Two varieties of Histoplasma cause human histoplasmosis. The…
The aspergilli are ubiquitous fungi whose normal ecological niche is that of a soil saprophyte that recycles carbon and nitrogen. The genus Aspergillus contains approximately 250 species, but most human disease is caused by Aspergillus fumigatus , A. flavus ,…