The fungal kingdom includes as many as 6 million species (1) and is remarkable in terms of the breadth and depth of its impact on global health, agriculture, biodiversity, ecology, manufacturing, and biomedical research.More than 600 fungal species are associated with humans, either as commensals and members of our microbiome or as pathogens that cause some of the most lethal infectious diseases(2–4). Individuals with weakened immune systems are the most vulnerable, but otherwise healthy individuals are also at risk from well-known and emerging pathogens, especially in situations in which infection involves a large inoculum. With the global increase in the incidence of invasive fungal infections and the emergence and spread of fungal pathogens resistant to all current classes of antifungals, these organisms pose an acute threat to human health (2–5). The full extent of this threat has not been possible to measure directly because there were no reporting requirements. A signal that matters may be improving came in 2016, when the World Health Organization declared mycetoma, a debilitating tropical fungal affliction of the extremities, to be a Neglected Tropical Disease, thus initiating work on surveillance, prevention, and control. Plans for strengthening the detection and monitoring of, and response to, mycotic diseases as well as implementation of antifungal resistance surveillance in invasive mycosis in the Americas are being developed.
Fungal diseases in humans have been increasing coincident with the advent of revolutionary new medical therapies, including antibiotics, immunosuppressive therapies, and indwelling medical devices. The first descriptions of candidiasis, a systemic yeast infection, were reported in the 1950s after antibiotics eliminated the helpful bacteria in our systems that keep the Candida fungus in check. The 1950s also saw the commencement of steroid use, the development of chemotherapy, and the introduction of indwelling catheters that pierce the skin, thereby providing a conduit that defeats skin defenses and enables microbes to cross into the interior. These factors helped fungal pathogens exploit humans as never before; it is remarkable that systemic fungal infections are not more common in humans.