The workers would be tested periodically. As simple as that. In Nevada, women who test positive for AIDS are literally not allowed to work at all. If they do, there are harsh legal implications (both for the brothel owner adn the worker). Illegal prostitutes (whether in brothels or on the streets) do not have to get tested and are not required to wear a condom.
In the countries in which sex work is legalized, workers in the sex industry have health care readily available to them, and it is mandatory for them to be tested for sexually transmitted diseases once every week or so, so as to prevent the spread of sexually transmitted diseases. And this has brought down the spread of STD's significantly.
HIV/AIDS is spread by reckless sexual practice. This aspect of transmission of disease is able to be controlled with establishments that can be held accountable for their quality of service. The clients, the call girls, and the girls handlers, all share the responsibility of health and safety. Examples of this can presently be seen in Amsterdam with window girls, and Nevada at the Bunny Ranch. Pornographic cinema also share strict regulation and professional level safety concerns.
Cleanliness, STD screening, drug testing, prophylactic use, visual genital inspection, pre and post pleasure hygiene, regular doctor checkups, are all measures that can be taken to prevent the spread of disease in these legal pleasure houses. This goes for the working girls and the clients themselves. Insuring the girls are clean creates rapport and quality in service, but clients have to be held to the same level of cleanliness. Legalization is the way to hold clients to a new light. Instead of stigmas of shame, and clients abusing the girls they visit, regulations make these service transactions respectable and therefore safer.
It gives prostitutes legal backing to insist clients use condoms, or be subjected to prior examination for STDs if they don't want to use condoms. In addition, prostitutes would be able to go to clinics to get themselves checked out for STDs.
That being said, while I support the right of willing prostitutes to ply their trade, I definitely don't support abusive and controlling pimps, and other people who force women/girls/boys/men into sexual slavery and prostitution. I find adultery/infidelity and cheating absolutely vile, but only the customer is to blame.
Within 4-6 weeks an HIV/AIDS tests will come back negative. Until the HIV/AIDS test comes back positive the infected will continue to spread. With the continuous spreading the demand for a cure will increase; however, a cure has not been found yet. How will we eliminate HIV/AIDS if it becomes a world wide epidemic?
To me it doesn't seem like that would affect the spread of HIV and AIDS at all. There would be guidelines and rules but there would still be people out doing it illegally to escape those rules. Plus who wants to go to a legal prostitute? Most of the people who go to prostitutes are in relationships and they would be more likely to get caught if they went to a legal institution. This question is kind of irrelevant anyway though. Prostitution will never be legalized. It is just wrong.
If prostitution was legalised then it would encourage more people to do it. If more people are having sex than the risk of HIV/AIDS is increased. Also, what happens if teenagers start doing it?