COVID Induced Functional Exhaustion and Persistently Reduced Lymphocytes as Vital Contributing Factors for Post-COVID Rhino-orbital and Cerebral Mucormycosis in Patients with Diabetes: Report from the Indian Sub-continent

The current pandemic of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is a global, unanticipated public health crisis. Another emerging challenge is the prevalence of "black fungus", or mucormycosis, among patients who recovered from COVID-19 infection. A retrospective study was conducted on 12 patients in a post-COVID recovery phase who developed mucormycosis. The study parameters evaluated lymphocyte count, CD4+ T cell status, and associated systemic co-morbidities for the patient, namely diabetes. The interventions during the treatment for COVID were also recorded to include administration of oxygen, ventilator assistance (invasive and non-invasive)/oxygen support, and steroid use. The possible relationship between low lymphocyte and CD4+ counts with diabetes and fungal growth was evaluated. It was observed that the majority of the patients who had a positive history for diabetes with low lymphocyte and CD4+ counts were more susceptible to opportunistic fungal infections. Most of the patients, but not all, had a history of receiving oxygen or assisted ventilation, as well as steroids, during the treatment for COVID infection. These interventions may be considered as accessory contributing factors for fungal infection. Post-exposure to SARS-CoV-2, therapies should be targeted at prevention of functional exhaustion of lymphocytes and maintaining optimal lymphocyte and subset counts in susceptible hosts for the prevention of opportunistic fungal infections. The relationship between functional exhaustion of the lymphocyte, diabetes, and COVID mandates further research.