Fungi are diverse and complex eukaryotic organisms with unique characteristics, such as a cell wall composed of chitin and glucans. Most fungi develop as hyphae, multicellular, filamentous and septate structures, which can form a circular mycelium. Fungi have a high metabolic capacity, allowing them to use various substrates for growth and reproduction, depending on nutrients, temperature, pH and humidity of the substrate. The true biodiversity of the fungal kingdom is underestimated, with only about 5% formally classified. A peculiar group of fungi is the entomopathogenic, capable of infecting insects and acting as biological control agents in agriculture. Cordyceps is an example of an entomopathogen with tropical distribution, capable of infecting carpenter ants to alter their behavior. Some studies highlight the possibility of a pandemic similar to that represented in TV series, such as the one that shows Ophiocordyceps capable of transforming ants into “zombies”.
Fungi are important for life due to their presence in diverse habitats and biological processes, such as nutrient cycling and the decomposition of organic matter in the soil. Furthermore, fungi produce secondary substances with significant commercial use in food, medicine, biodegradation and wastewater treatment. They are also used in the industrial production of food, alcoholic beverages and pharmaceuticals. Some fungi are necessary for bioremediation in environments contaminated with difficult-to-degrade compounds such as pesticides, industrial waste and heavy metals. However, many mycotoxins are responsible for severe symptoms when consumed or released into the host.
The kingdom of fungi is classified into phyla based on morphological and reproductive characteristics. Spore dispersal helps maintain the species and increase genetic variability. Some fungi are adapted to disperse during dry periods, which can be problematic for agriculture and cause respiratory allergies. Ascomycota is the main phylum of fungi that cause disease in humans, with genera such as Aspergillus, Penicillium, Saccharomyces, Candida and Cryptococcus. To establish infections in humans, pathogens must penetrate host barriers, adapt to human tissue, and evade the immune system. Virulence factors and mycotoxins play a role in disease progression. Many fungi are opportunistic pathogens and can invade tissues when host barriers are not functioning properly. Central nervous system infection is difficult to treat with current available treatments.
Fungal infections are a global health problem due to high mortality and socioeconomic consequences, mainly affecting the elderly and immunocompromised individuals. Allergic fungal infections are triggered by pre-existing conditions such as asthma and sinusitis, while dermatophytic infections affect the skin, nails and hair. Some types of fungal infections can spread to other tissues and cause serious illness. The excessive use of fungicides in agriculture and the use of antibiotics and corticosteroids in hospitals have led to the development of fungi resistant to antifungal drugs. Candida albicans and Candida auris are the most common species of fungi that cause infections in humans. Aspergillus fumigatus is a fungus that can cause allergic diseases and serious lung infections, while fungi in the genus Mucorales can cause mucormycosis. The COVID-19 pandemic has increased the prevalence of some fungal infections, especially in immunocompromised patients. The diagnosis and treatment of fungal infections are challenging, and the development of new therapies and more accurate and rapid diagnostic methods is necessary.
Fungal infections of the central nervous system (CNS) have become increasingly common in the last two decades due to the virulence of the strains and the host’s immune response. Interaction with the blood-brain barrier (BBB) is essential for the pathogen to reach the nervous system directly or indirectly. Diagnosis depends on a combination of procedures, and treatment still has a low prognosis, reinforcing the need for rapid diagnosis and correct identification of the causative agent. Fungal infections have been a global health problem due to high mortality, but are not yet considered a fungal pandemic.
