It’s been scientifically proven that anal sex is riskier than vaginal sex when it comes to HIV. Eighteen times riskier to be exact. There are two reasons for this. First, the cells in the ass are much more susceptible to HIV than cells in the vagina. Second, both semen and rectal mucosa (the lining of the ass) carry more HIV than vaginal fluid. Combine this with the fact that gay and bi guys have much more anal sex than straight guys, and you’ve got yourself a lot more risk right there.
In a recent Auckland study, 1 in 15 gay and bi guys were found to have HIV. So, if you’re a guy hooking up with other guys, you’re more likely to meet someone who has HIV (and according to that same study, there’s a 20 percent chance that person with HIV doesn’t know it yet).
The reality is that there are less gay and bi guys than there are straight men and women. So when you’re meeting a guy for casual sex, the pool of people you have to choose from is smaller. This makes gay and bi guys much more closely connected, sexually, than the rest of the population. It also allows HIV and other STIs to spread quickly among us.