The guidance was originally put into place over concerns that MSM have a higher risk than the average person of having human immunodeficiency virus (HIV). In the U.S., the estimated lifetime risk for HIV infection among MSM is one in six. In comparison, heterosexual men have a one in 524 risk and heterosexual women have a one in 253 risk. The three-month marker is currently in place “because that was felt to be an adequate time to wait for HIV antibodies to develop in someone who is newly infected,” Richard Watkins, MD, an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, told Verywell. If a man who has sex with men is newly infected with HIV and waits three months to give blood from his last sexual encounter, testing should be able to detect the virus at that point, he explained. To read the full story.