Vienna HIV Infection Via Sex Study

We will include individuals at high-risk for HIV acquisition, i.e. HIV-negative MSM and transgender individuals who (i) do not use condoms consistently with casual partners and/or with HIV-positive partners who are not on treatment and/or (ii) recently acquired an STI and/or (iii) recently used PEP and/or (iv) frequently engage in 'chemsex' within the past 12 months Important clinical information on possible vectors for transmission (including but not limited to high-risk sex practices and sexualized drug use), use of HIV pre-exposure prophylaxis, incidence of sexually transmitted infections will be assessed and laboratory parameters will be obtained from blood, urine and mucosal secretion.