Diagnosis of HIV infection: a study of the viro-immunological picture, viral sub-types and drug resistant mutations, even in minority quasispecies, in adult subjects followed in Veneto in the January 2020 – November 2025 time period

Study Rationale: HIV infection, despite progress in antiretroviral therapy (ART), remains a global challenge, complicated by the virus's genetic diversity and the spread of transmitted drug resistance mutations (TDRMs). In Italy, migrations and changes in patient characteristics at diagnosis have been associated with a progressive increase in non-B subtypes and new patterns of resistance to the drugs used, making continuous monitoring necessary to optimize therapeutic and care strategies. Study Aim: This study aims to analyse the characteristics of patients at the time of HIV infection diagnosis, with reference to age, sex, nationality, immunological and virological status for HIV, prevalence of transmitted drug resistance mutations (TDRMs), distribution of HIV-1 subtypes, and presence of co- infections. Patients followed in several centers in the Veneto region will be studied, focusing on the period between January 1, 2020, and October 31, 2025. The main objective is to update data from previous similar studies conducted in the same geographical area, and help evaluating the therapeutic strategies adopted for the first antiretroviral treatment.