30 years into an epidemic, doctors have reached a breakthrough in HIV/AIDS treatment: by having HIV positive people take medication early and often, the risk of them transmitting the disease to others can diminish by as much as 96 percent, an astonishing number.

The scientific community has taken note of this sea change, with a prominent Canadian HIV/AIDS researcher announcing ahead of a world HIV/AIDS summit that a shift to preventative care has become an urgent implementation priority for doctors and policymakers. Dr. Julio Montaner of Vancouver's B.C. Centre for Excellence in HIV/AIDS referenced the double hat trick of prevention: not only does early treatment lower mortality rates for those with the disease, it shields others from contracting it.

To be certain, it is welcome news in the battle against a global scourge of a disease. But it also raises a complex ethical dilemma: should doctors be able to override a patient's wishes and make him or her begin treatment in order to protect others?

Doctors must respect individual choice, and many patients are reluctant to begin treatment out of wariness of cost or side effects. At the same time, from a utilitarian standpoint -- one that seeks to do as much good to as many people as possible -- one could argue that preserving the health of the population at large should take precedence.

It was unthinkable when we had this debate in the early 1980s, and it's unthinkable in 2011, Dr. Myron S. Cohen of the University of North Carolina told the New York Times. He noted that such questions arose in the early days of HIV/AIDS, when it was still a relatively new disease surrounded by misconceptions and stigmatization, and called the idea of forcing someone to go onto medication medieval and a violation of civil rights.

For the sake of comparison, imagine that a deadly infectious disease has struck a crowded urban center. Police choose to impose a quarantine, herding those who have already fallen ill into a building that isolates them from others. A horror movie? Hardly -- the Centers for Disease Control and Prevention has guidelines for just such a case.

The difference may lie in how HIV/AIDS is transmitted. Dr. Thomas Frieden, former head of the CDC, resorted to a quarantine during a tuberculosis outbreak, and said the contrast between the two illnesses provides a good starting point for debate.

I see a bright line between tuberculosis, which can be passed standing next to someone in an elevator, and H.I.V., which usually requires consensual sexual activity, he said.