Increases in condomless chemsex associated with HIV acquisition in MSM but not heterosexuals attending a HIV testing center in Antwerp, Belgium

a Proportion of Helpcenter attendees reporting ever had sex under influence of ecstasy/cocaine/amphetamines/GHB and b use of ecstasy/cocaine/amphetamines/GHB at a party in past 6-months in men who have sex with men (MSM; black) and heterosexuals (grey) between 2011 and 201