COVID-19-Associated Fungal Co-Infections: Pathogenesis, Diagnostics, Biomarkers, and Therapeutic Strategies

From a health perspective, the 21st century has witnessed the emergence and global impact of several major viral diseases, most notably coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2, which has been associated with a substantial burden of secondary fungal infections. Patients suffering from COVID-19 illnesses frequently developed fungal co-infections, which can worsen clinical outcomes and complicate therapeutic efforts. Hospitalized individuals with viral infections are particularly susceptible to invasive fungal pathogens, including Aspergillus, Candida, and Mucorales species. The co-pathogenesis between respiratory virus and fungi is complex, involving dynamic interactions among the pathogens and the host immune system. Opportunistic fungal infections were found to be more prevalent in COVID-19-infected individuals, who require mechanical ventilation, have diabetes, or exhibit neutropenia. This review aims to provide a comprehensive overview of fungal co-infections associated with COVID-19 disease, with a focus on their pathogenesis, biomarkers, diagnostic approaches, and potential treatment strategies. Overall, the available evidence indicates that viral-induced immune dysregulation, epithelial barrier damage, and clinical risk factors contribute to the development and severity of fungal co-infections in COVID-19 patients. Early recognition using reliable biomarkers and standardized diagnostic approaches, together with timely and pathogen-directed antifungal therapy, are essential for improving clinical outcomes.