A silver bullet to defeat HIV/AIDS still doesn’t exist, but the world is getting closer.

An international study released this week found that transmission of the virus can be nearly eliminated if patients are simply given drug therapy as early as possible.

The trial was among 1,763 couples where one partner was infected. The couples were split into two groups - in one group the infected partners had received anti-retroviral drugs immediately upon diagnosis, in the other, the infected partners had begun therapy later.

Over the course of six years, researchers found that those who had started treatment early were 96 percent less likely to transmit the virus to their partners than those who had begun treatment later. The data was so overwhelming that the study was terminated years ahead of schedule.

The results are the first to prove what HIV/AIDS experts already suspected - that immediate treatment offers major health benefits. They also back San Francisco public health officials’ much-debated recommendation from last year that people should be treated as soon as possible after their diagnosis.

“The pendulum has really swung towards early treatment,” said Dr. Grant Colfax, director of HIV prevention for San Francisco’s Public Health Department.

It’s poignant that the study’s release is happening just weeks before the 30th anniversary of the first reports of HIV in the United States.

“This year there have been a lot of positive signs in terms of turning the epidemic around,” Colfax said. “Maybe in another 30 years, (HIV) won’t be around.”

In the meantime, this study poses a new challenge to public health officials. The evidence is clearly starting to show that it’s much better to treat patients earlier, but from where will the money come?

Anti-retroviral medications have made huge strides in the past five years. The side effects are less debilitating and the drugs are more widely available in poor countries that have been racked by the epidemic.

Unfortunately, they’re still very expensive. Many poor countries, already struggling to deliver therapy to those with full-blown AIDS, will probably conclude that they can’t afford to launch early treatment programs for people who aren’t already sick.

That would be a mistake. Yes, anti-retroviral medications are pricey - but what are really expensive are new HIV infections. Early treatment offers enormous returns for patients’ health and productivity, and now, it appears, that benefit extends to their partners as well. It doesn’t come cheaper than that.

This article appeared on page A - 9 of the San Francisco Chronicle