Mucormycosis (Black fungus): An Emerging Fatal Mycosis of21st Century- An Overview of History, Epidemiology, ClinicalSpectrum, Diagnostic Approaches and Treatment

Abstract

Mucormycosis (zygomycosis, black fungus), is an emerging, noncontagious, opportunistic, life-threatening disease of sinuses, lungs, skin and brain of immunocompromised individuals, caused by the mucoraceous fungi. Friedrich Küchenmeister, a German physician, discovered the first case of mucormycosis in 1855. The fungal infections
of humans, called mycoses, are a growing global health concern affecting more than one billion people causing over 3.75 million deaths each year. Due to the global surge in mucormycosis incidence with a marked increase in India and China especially among patients with uncontrolled diabetes mellitus (DM), it is designed as an emerging fatal mycosis of the 21st century. Globally, 39 fungal species belonging to 11 genera of Mucoromycetes (Mucoromycota) are involved in mucormycosis.
Seventy-five percent incidences of mucormycosis are caused by the 3 genera Rhizopus, Mucor, Lichtheimia, and Rhizopus arrhizus (R. oryzae) alone is the main causative agent involved in 50 % of all cases of mucormycosis globally. The mortality rate is much higher in mucormycosis, considered to be an emerging mycosis, compared to aspergillosis and candidiasis, the two other fatal emerging mycoses. The infection mainly occurs when the fungal spores (sporangiospores) are inhaled by humans from the environment of the saprophytic mucoraceous fungi occurring in soil and decomposing plant residues. The inhalation is the most common mode of transmission compared to inoculation and ingestion. The epidemiology and mortality, despite antifungal therapy, has shown an exponential rise, the disease named as “black fungus” in 2021 following the second wave of COVID-19 pandemic. Prevalence of mucormycosis in India is nearly 80 times higher than global picture. Histopathological microscopic examination of stained biopsy samples for nonseptate wide hyphae and identification of fungi based on fungal culturing are often used
in diagnosing mucormycosis. Molecular (PCR- based fungal DNA), qPCR kits, protein homolog in spore coating, serology, and imaging techniques are the other diagnostic techniques. Early diagnosis and prompt initiation of antifungal therapy along with surgery and control of risk factors are needed for successful management of mucormycosis. Antifungal drugs to treat mucormycosis include: amphotericin B, Isavuconazole, posaconazole and itraconazole, the former two recommended by
the USFDA for the primary therapy. Amphotericin B, preferably liposomal amphotericin B (L- AMB), is the drug of choice globally for managing mucormycosis of various types: rhino-orbital-cerebral, pulmonary, gastrointestinal, cutaneous, renal, disseminated and COVID-19-associated mucormycosis.