Virulence and pathogenicity of secondary fungal infections.

Fungal infections pose a significant global health threat, particularly among immunocompromised individuals facing life-threatening complications. The severity of secondary fungal infections is driven by the expression of virulence factors in immunocompromised individuals. The COVID-19 pandemic has highlighted the susceptibility of immunocompromised patients to secondary fungal infections, prompting a closer examination of the underlying mechanisms. This review provides a comprehensive overview of the virulence mechanisms of major fungal pathogens (Aspergillus, Candida, and Mucorales) in COVID-19-associated secondary infections. The review systematically categorizes key virulence factors, including thermotolerance, adhesins, hydrolytic enzymes, mycotoxins, and biofilm formation, and explores their interplay with the host's immune status, particularly under corticosteroid therapy. Focusing on the intersection of fungal pathogenesis and COVID-19, the article examines molecular mechanisms underlying Aspergillus, Mucorales, and Candida pathogenicity, including iron metabolism, spore coat proteins, and immune evasion strategies. Followed by linking the molecular mechanisms to therapeutic strategies and clinical outcomes.