In the U.S., you may soon have to opt out of HIV testing rather than opting in:
Seven years ago the [United States Preventive Services Task Force] came to a different conclusion on the question of screening for HIV, believing that the benefits were insufficient to recommend it. Since then, however, evidence has accumulated that treating people early in the course of their infection not only prolongs their life but reduces spread of the infection.
One notes that widespread testing was responsible for the containment of syphilis when it was an incurable and fatal disease. This was known. Nevertheless, a good many people fought tooth and nail against such a program for AIDS and are unquestionably guilty of thousands of deaths.