A study revealing the sexual habits of Swedes has cast light on the need to focus HIV prevention campaigns on a small minority of people with many sex partners, rather than on the general public, researchers said. The 1996 survey of 2,810 Swedes ages 18 to 74 years, which appears in today's issue of Nature, provides a startling example of a "sexual contact network" in which people are unwittingly connected. The study demonstrates how Swedes are linked via a tiny number of men and women who have had many sexual partners. "This small, very small fraction of people with a really disproportionate number of sexual contacts is responsible for the spread of epidemics of sexually transmitted diseases," said Luis Nunes Amaral, co-author of the study.

According to the report, Swedish men have had on average 15 sexual partners while women have had seven. But 10 percent of the most sexually active men accounted for 48 percent of all contacts and one man alone said he had had 800 partners. The top 1 percent among sexually active men accounted for nearly one in six of all contacts in the network. Among women, 10 percent of the most sexually active accounted for 40 percent of all contacts. The top one percent of sexually active women accounted for one in 10 of all contacts. The most prolific was a woman who had had 100 partners, Amaral said.

The data in the survey were used by Amaral, sociologists at Stockholm University, and others to build a picture of "vulnerable nodes" within a sexual network that could accelerate the spread of diseases. "What this tells us is that the way to control the spread of sexually transmitted epidemics is to control the behavior of these people," Amaral said. "If you remove these people from a network, then you change this from a network into smaller clusters. If you have small clusters, you cannot have an epidemic. So it is important to remove these people from the network by changing their behavior." The study did not detail the safe sex practices of those surveyed.

Back to other CDC news for June 21, 2001

Previous Updates | Search the CDC archive