Sexually transmitted infections (STIs, formerly referred to as STDs) are a group of infections that are transmitted through sexual activity. Participating in unprotected sex will increase the chance of acquiring any of these infections. From the WHO website: “Each year, there are an estimated 357 million new infections with 1 of 4 STIs: chlamydia, gonorrhoea, syphilis and trichomoniasis. More than 500 million people are estimated to have genital infection with herpes simplex virus (HSV). More than 290 million women have a human papillomavirus (HPV) infection”.
Other high-risk activities, such as unprotected sex and drug use (particularly intravenous drug use) can transmit most of these infections as well. The unfortunate reality is that many people using illicit substances also frequently engage in unprotected sex, greatly increasing their overall odds of acquiring one of these infections. The reasons so many drug addicts or alcoholics are more likely to have unprotected sex are numerous, and include the lowering of inhibitions while intoxicated, as well as overt trading of sex for money or drugs.