The estimated number of people living with undiagnosed HIV infection and CD4 count < 200 cells/mm3 in Italy was 2,467 (95% CI: 2,052–3,145) in 2012, 2,456 (95% CI: 2,027–3,151) in 2013, and 2,524 (95% CI: 2,075–3,246) in 2014 (Table 3). This evidence concerns the gene CD4 and HIV infectious disease.