I agree completely with the quarantine for people working outside of the country. You can't be as certain with tests from Also HIV tests should only be accepted from legitimate places. Also all work related sex should be well documented if something like this happens again. Of course this can't help for people having sex outside of work or for the many people in the industry who escort outside of work - there are a lot of people with HIV in USA
The safest option would be that everyone have a test before every job they do but even then you would have to hope that they don't have sex outside of work in between the test and the job