Opportunistic infection has been categorized according to CD4+ counts as follows: Mycobacterium tuberculosis was found in all CD4+ counts; Coccidioidomycosis was in CD4+ counts <250cells/mm3; Pneumocystis jiroveci pneumonia and mucocutaneous candidiasis were in CD4+ counts <200cells/mm3; Histoplasma capsulatum was in CD4+ counts <150cells/mm3; C. neoformans, Cryptosporidiosis, Herpes simplex viruses, Microsporidiosis were in CD4+ counts <100cells/mm3; and C. neoformans, Cryptosporidiosis, and Cytomegalovirus, T. gondii, and Bartonellosis were in CD4+ count <50cells/mm3 [15]. This evidence concerns the gene CD4 and Opportunistic infection.