The Supporting Cast – High and Medium Priority Fungi. While the “critical priority” fungi demand immediate and urgent action. The pathogens in the “high” and “medium” priority groups should not be overlooked. These fungi represent a diverse array of public health challenges, from regionally endemic diseases to opportunistic pathogens that are gaining a foothold. They are a constant reminder that the fungal threat is broad, dynamic, and requires continuous vigilance.
The High Priority Fungi
Includes pathogens that pose a significant threat. And also have serious unmet needs in terms of diagnosis and treatment. Among them is Nakaseomyces glabrata (formerly Candida glabrata), a commensal yeast that has become a leading cause of candidiasis. Particularly in hospital settings. It is known for its intrinsic resistance to fluconazole, the most widely used antifungal. Thus making it a difficult pathogen to treat and contributing to its high mortality rates. Also in this group is Histoplasma spp.. This is a fungus endemic to certain regions of the Americas and Africa. It causes histoplasmosis, a systemic infection that can be life-threatening in immunocompromised patients. The lack of awareness and quality diagnostics often leads to delayed diagnosis and poor outcomes.
The high-priority list also includes
Eumycetoma causative agents, a group of fungi that cause a debilitating, chronic, and deeply disfiguring infection of the skin and underlying tissues, primarily in tropical and subtropical regions. The disease is a leading cause of disability and has few effective treatment options, making it a major public health issue in affected areas. Mucorales is another group of high-priority molds responsible for mucormycosis, a devastating and often fatal disease that gained notoriety during the COVID-19 pandemic. With an extremely high mortality rate, often exceeding 50%, mucormycosis is an aggressive and life-threatening infection. Lastly, Fusarium spp. are a group of molds that cause difficult-to-treat invasive fusariosis, particularly in severely immunocompromised patients. These pathogens are often resistant to multiple antifungals, making effective therapy a significant challenge.
The Medium Priority fungi
A wide range of pathogens that, while not currently at the same level of global urgency, still represent significant threats that warrant ongoing attention. This includes Pneumocystis jirovecii, an opportunistic fungus that causes a severe form of pneumonia, primarily in people with HIV/AIDS. While advances in HIV treatment have reduced its incidence, it remains a critical cause of illness in this population. Another is Coccidioides spp., the cause of coccidioidomycosis, also known as Valley Fever. This fungus is endemic to the arid regions of the Americas and can cause a severe respiratory and systemic disease. The list also includes pathogens like Scedosporium spp., molds with high rates of antifungal resistance; Cryptococcus gattii, a cousin of C. neoformans that can cause disease in healthy individuals; and Talaromyces marneffei, an endemic fungus in Southeast Asia.
By including these pathogens, the WHO emphasizes that the fungal threat is not limited to a select few species. It highlights the importance of a broad, comprehensive approach that includes a variety of fungi, from globally prevalent hospital pathogens to endemic species that affect specific geographic regions. This tiered approach ensures that resources are allocated effectively, focusing on the most critical threats while simultaneously promoting vigilance and research for a wider range of fungal diseases.