HSPA5 and infection: GRP78 acts as a host receptor for fungal pathogen Rhizopus oryzae, the most common etiologic species of Mucorales, and mediates the invasion and damage of human endothelial cells [81]; GRP78 binds with Pneumocystis carinii on the cell surface of lung epithelial cells, mediating the attachment [82]; these studies suggest that GRP78 might be involved in cases of co-infection and secondary infection in COVID-19 patients.