CHICAGO - Nearly 25 years after a news magazine declared that an epidemic of genital herpes threatened to undo the sexual revolution, a new study finds an encouraging decline in the percentage of people infected with the herpes virus.

In 1982, a Time cover story headlined "The New Scarlet Letter" sounded an alarm that seems almost quaint now compared to concern over another sexually transmitted lifetime infection, the AIDS virus.

The new study shows a 19 percent drop since 1994 in the percentage of Americans ages 14 to 49 testing positive for herpes type 2, the most common cause of the recurring painful sores of genital herpes. The declines were especially pronounced among young people.

The findings, appearing in today's Journal of the American Medical Association, represent solid biological evidence of a decrease in risky sexual behavior among adolescents, said lead author Dr. Fujie Xu of the Centers for Disease Control and Prevention.

"Overall, this is good news. There is a decrease occurring among all youth, males and females, and in all racial groups," Xu said. "That's very encouraging."

But herpes is still uncomfortably common. Despite the decline, blood tests of more than 11,000 people found 11 percent of men and 23 percent of women carry the genital herpes, or type 2, virus. Among people in their 20s, the infection rate was almost 11 percent.

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