I think that smaller scale versions of this are feasible- say, a bathhouse that required all members to take a HIV test every n months, and only allowed entry to people with negative results- but as with most things in public health, larger scales have larger benefits.
This kind of thing is standard practice among porn studios...
A post from Gregory Cochran's and Henry Harpending's excellent blog West Hunter.
The commenter Ron Pavellas adds:
The Wasserman Test.