CD4 and COVID-19: Although there is no direct relationship between the genomes of the two viruses [8], the results of this study suggest that for COVID-19 patients with decreased CD4+ T lymphocyte numbers in their peripheral blood, the protease inhibitors used to treat human immunodeficiency virus (HIV) infection, such as lopinavir and ritonavir, are also worth trying and studying to improve the outcome of patients with COVID-19.