Association of COVID with Mycosis in General

Background: The COVID-19 pandemic caused by SARS-CoV-2 is a respiratory disease which created havoc worldwide, was accompanied by another peculiar, otherwise rare, secondary fungal infection Mucormycosis which was observed at exceptionally high incidence in India during the second wave of COVID-19. The article explores possible links between the two infectious diseases to understand a higher-than-normal occurrence of Mucormycosis in COVID-19 patients. Coronavirus enters the patients through ACE-2 and many other receptors like- NRP-1, TfR, CD-126, and CD-26. Virus bind to cells possessing these receptors and affect their proper functioning, disturbing homeostatic metabolism and resulting in conditions like hyperglycemia, Diabetic Ketoacidosis (DKA), low serum pH, iron overload, anemia, hypoxia, and immunosuppression as explained in the article. All these outcomes provide a very supportive environment for the attack and spread of Mucormycosis fungi. The major receptor for Mucormycosis in humans is the GRP-78. Its expression is upregulated by coronavirus entry and by hyperferritinemia, hyperglycemia, and acidic conditions prevalent in COVID patients, thus providing an easy entry for the fungal species. Upregulation of GRP-78 furthermore damages pancreatic β-cells and intensifies hyperglycemia, showing quite a synergic relationship. Inordinate rise of Mucormycosis cases in India might be explained by facts like- India possessing a large proportion of diabetic patients, emergence of a very deadly strain of coronavirus- Delta strain, higher doses of steroids and antibodies used to treat patients against this strain, overburdened health care services, sudden much higher need of oxygen supply and use of industrial oxygen could explain the Mucormycosis outbreak observed in India during the second wave of COVID-19. Objective: The present review discusses the functional interdependence between COVID-19 and Mucormycosis and summarizes the possible synergic links between COVID and Mucormycosis. Conclusion: The receptors and metabolic pathways affected by COVID-19 result in severe physiological conditions- hyperglycemia, DKA, anemia, iron overload, immunosuppression, and hypoxia. All these conditions not only increase the expression of GRP-78, the major receptor for entry of fungi but also play a crucial role in providing quality media for Mucormycosis fungus to establish and grow. Hence explains the fungal epidemic observed in India during the second wave of COVID-19 in India.