This article states the U.S. Preventative Task Force has finally decried every adult 15 + needs to be tested for HIV at last once in their life. The reasons they cite are sound & they mention the amount of infected people who are unaware they're +.
The 1 time thing is only for people with no recognizable risk factors. There are too many instances when people fail to recognize the risks of a given situation. They might very well have been taking part in a risky behavior & never viewed it as such. Therefore they never got tested.
This could prove enlightening for a lot of people.
Cya...