For the seventh year in a row, thousands of scientists from around the world gathered last week to share their research on a disease that frustrates and fascinates them. Although the International Conference on AIDS in Florence was less politicized than in past years, there were demonstrations over a U.S. immigration policy that bans anyone carrying the AIDS virus. There were gloomy predictions that by 1995, 115 million people will be infected worldwide. And some studies suggested it's easier to get AIDS through heterosexual intercourse than most people think. But the conference offered good news, too: researchers understand better why some people carrying the virus remain free of symptoms for many years - and new drugs hold out the promise of prolonging lives.
An estimated 8 million to 10 million people are infected with the AIDS virus, says Dr. James Chin, head of the World Health Organization's AIDS surveillance unit; more than half live in sub-Sahara Africa. By 1995, Chin says, newly diagnosed cases will likely plateau in the industrialized world, but transmission will explode in developing nations. During the next couple of decades in the Third World, Chin predicts, "AIDS will become the leading cause of death for adults in their most productive years."
In the developing nations AIDS is spread most often by heterosexual intercourse. Initially researchers believed the virus was harder to transmit by vaginal sex than anal sex, where rectal bleeding gives it direct entry to the bloodstream. But researchers from Harvard University's Dana Farber Cancer Institute reported evidence of what scientists had long suspected: even very small concentrations of the virus can be transmitted directly through mucous membranes. Dr. William Haseltine's team discovered the virus in a type of cell found in the linings of the rectum, vagina and mouth. Although AIDS transmission through deep kissing (with exchange of saliva) is theoretically possible, says Haseltine, "most people in public health think the risk is a small one."
Viruses lurking in mucous membranes, away from the bloodstream, may be more difficult to zap with drugs. But at least one drug, AZT, has lengthened the lives of many people who are HIV positive. Several researchers reported that combining AZT with the experimental drugs known as DDC and DDI substantially increased survival rates.
Physicians have been tantalized by the puzzle of people with longstanding HIV infections who haven't developed symptoms. Dr. Jay Levy of the University of California, San Francisco, discovered that their immune systems naturally produce a substance that temporarily halts replication of the virus. It seems able to fend off the virus's ravages for as long as a decade, says Levy, and could be useful in developing effective drugs.
As the conference ended, there was much apprehension among participants over whether they would meet again in 1992. Many said they won't attend next year's meeting in Boston if the restrictive U.S. immigration policy isn't changed; conference organizers may even cancel it. The U.S. Public Health Service recently recommended eliminating all but active TB from the list of eight infectious diseases that preclude entry to the United States. So far, the Bush administration has rejected that advice. Like many other aspects of AIDS, the outcome of this conflict is still uncertain.