HIV positive patients should have to disclose that information to their employer due to insurance reasons, as well as provide a safe environment for other employee’s. If they have knowledge of the potential risk, then they can put in place planning and mitigation schemes in the event of industrial accidents, common infections, and exactly were to place someone with a limiting disability.
Medication has gotten a lot better. People aren't dying off like flies like they were in the 1990s as a result of the disease (perhaps where all the stigma comes from?). Most people who know they have HIV nowadays are probably healthier than those who don't have the disease, because they have regular doctor visits and generally take better care of themselves. HIV is not considered a "disability" anymore by medical standards. Probably some sectors of government still define HIV as a "disability" but the government has never been quick to catch on to these things... An employer would have a greater risk hiring a diabetic employee, but also everyone has their right to privacy.
People with an HIV infection have a right to privacy just like anyone else with a medical malady. No one has to disclose their cholesterol levels, heart murmurs, ear infections or flu vaccine status. Medical privacy is just that--everyone has a right to keep their health to themselves. No one should have to disclose to their employer they have HIV. The disease is transmitted through blood exchange, not through handshaking.