Patients with severe COVID-19 had marked violations of local (epithelial damage, ciliary clearance, etc.)and systemic immunity (lymphocytopenia, CD4-cytopenia, etc.)due to the viral infection itself and the use of GCS and immunosuppressants, which can be accompanied by bacterial and fungal superinfections, including IA [14,15,16]. Here, CD4 is linked to viral infectious disease.