For the first time since the start of the AIDS epidemic, researchers are reporting a decline in the percentage of men and women infected with HIV in southern Africa. The findings are from a study conducted in eastern Zimbabwe, where researchers speculate the AIDS prevention message is starting to have an effect.

The study was conducted in Zimbabwe's eastern province of Manicaland, and involved 10,000 men and women between the ages of 15 and 54.

A six-month-old HIV positive baby is held up by his mother, right, who did not want to be identified, in a Bulawayo shelter (file photo)

At the beginning of the study in 1998, the HIV prevalence, or percentage of people in the region living with the AIDS virus, stood at 23.5 percent. At the study's conclusion, the overall prevalence had dropped to 20 percent.

The steepest decline was among young women between the ages of 15 and 24. The percentage of women who were infected with the AIDS virus dropped from 16 percent  to 8 percent, a 50 percent reduction.

There was also a 23 percent drop in HIV prevalence among young men between the ages of 17 and 19.

The results of the study are published in the February 2 issue of the journal Science.

The study's lead author, Simon Gregson of the Imperial College in London, believes the AIDS prevention message finally got through to young people on a personal level.

"It got to the point where almost everyone in these communities already knows somebody who has gotten very ill with AIDS or died from AIDS," he said. "So, the whole thing has become very real to people. And people realize that this is not something which only happens to those involved in prostitution or people who are very promiscuous. It is something that can happen to everybody. So, unless they are very careful themselves, there is a chance they will get infected."

Gregson says factors that contributed to the decline in Zimbabwe's HIV prevalence include information on how to prevent the spread of the virus to pregnant women, the widespread availability of AIDS counseling, HIV testing programs, and inexpensive condoms.

Gregson is hopeful the downward trend will continue.

"If those people can manage to sustain their sexual behaviors as they get older, then that should gradually spread through the population over time," he said. "And the overall level of HIV rates will come down. That is certainly hoped that that would be the case. But it's certainly early days at the moment."

To experts, the Zimbabwe experience proves the importance and success of prevention strategies in countries in southern Africa where HIV prevalence has remained stubbornly high.

Writing in Science, Richard Hayes of the London School of Hygiene and Tropical Medicine says despite the lure of anti-viral drugs, prevention measures must remain a top priority for international public health.

"Otherwise, we are going to have an ever-increasing number of infected people and it is going to be very difficult to sustain treatment for all those people," he said.