Fungal pathogens and infections are an increasing global public health concern, particularly for those with underlying health problems or a weakened immune system.
Cases of invasive fungal diseases are on the rise and access to quality diagnosis and treatment is limited, and there are concerns over the emergence of strains resistant to antifungal medicines.
The World Health Organization (WHO) recently published its first-ever list of fungal ‘priority pathogens’ – 19 fungi representing the greatest threat to public health.
They are categorised into three groups – critical, high and medium – ranked based on their public health impact and emerging antifungal resistance risk.
The top critical priority group includes Cryptococcus neoformans, Candida auris, Aspergillus fumigatus and Candida albicans.
Cryptococcus neoformans is a fungus that can be found in the environment and can cause infections if inhaled. Cryptococcosis initially affects the lungs but can spread to the central nervous system and blood. Vulnerable groups include individuals with a weakened immune system and HIV patients.
Candida auris has high outbreak potential and has caused several hospital outbreaks, resistant to most antifungal medicines. Although treatment guidelines are well established, recommended antifungals are unavailable in many countries.
Aspergillus fumigatus is a common mould that can infect humans and mainly affects the lungs. It is becoming increasingly resistant to azole medicines, with a mortality rate of 47 to 88 per cent in azole-resistant infections.
Candida albicans produces no harm in healthy conditions but can cause infections with high mortality. Invasive candidiasis has an overall mortality of 20 to 50 per cent despite the available treatment.
Meanwhile, the high priority group includes Nakaseomyces glabrata (Candida glabrata), Histoplasma spp, eumycetoma causative agents, Mucorales, Fusarium spp, Candida tropicalis and Candida parapsilosis.
In the medium priority group are Scedosporium spp, Lomentospora prolificans, Coccidioides spp, Pichia kudriavzeveii (Candida krusei), Cryptococcus gattii, Talaromyces marneffei, Pneumocystis jirovecii and Paracoccidioides spp.
Currently, only four classes of antifungal medicines are available with a few candidates in the clinical pipeline. Most fungal pathogens lack rapid and sensitive diagnostics and those that exist are not widely available or affordable globally.
The invasive forms of these fungal infections often affect severely ill patients and those with significant underlying immune system related conditions.
During the COVID-19 pandemic, reports of invasive fungal infections increased significantly among hospitalised patients. As harmful fungi become more resistant to treatment, risk for development of more invasive forms of infections in the general population also increases.
Evidence also suggests the incidence and geographical range of fungal infections are expanding due to climate change.
“Emerging from the shadows of the bacterial antimicrobial resistance pandemic, fungal infections are growing, and are ever more resistant to treatments, becoming a public health concern worldwide,” said WHO Assistant Director-General for Antimicrobial Resistance (AMR) Dr Hanan Balkhy.
Despite the rising concern, fungal infections receive less than 1.5 per cent of all infectious disease research funding. As a result, quality data is scarce and most treatment guidelines are informed by limited evidence and expert opinion.
“We need more data and evidence on fungal infections and antifungal resistance to inform and improve response to these priority fungal pathogens,” said WHO Director of AMR Global Coordination Department Dr Haileyesus Getahun.
The report highlights strategies to generate evidence and prevent the development of antifungal drug resistance. “Countries are encouraged to follow a stepwise approach, starting with strengthening their fungal disease laboratory and surveillance capacities, and ensuring equitable access to existing quality therapeutics and diagnostics, globally,” added Dr Getahun.