CD4 and infection: In Italy, the data from the national surveillance system for HIV reveal that the incidence of the infection is 4.0 per 100,000 residents, lower compared to that reported in Western European countries and the European Union (6.2 new diagnoses per 100,000), but more than 60% of cases are diagnosed late, with a number of CD4 lymphocytes lower than 350 cells/μL [4].