The prevalence rate of herpes infections in the United States appears to be declining, according to a study released yesterday.
In the early 1990s, about 21 percent of Americans tested positive for herpes simplex virus type 2 (HSV-2), which causes genital herpes, Dr. Fujie Xu said in an article in the Journal of the American Medical Association.
This was about a third higher than the prevalence rate seen in the late 1970s.
However, in a 1999-2004 survey, 17 percent of the population tested positive for herpes.
This means that although genital herpes infections remain common, the trend toward higher prevalence rates “has been reversed,” wrote Dr. Xu, who works at the federal Centers for Disease Control and Prevention.
Possible explanations for the downturn include improved use of condoms, more careful selection of sex partners and sexual abstinence, especially among teens, she said.
Prevalence of the virus that causes “cold sores,” known as herpes simplex virus type 1 (HSV-1), also fell, from 62 percent to 58 percent. However, Dr. Xu said, there is evidence that genital herpes caused by HSV-1 may be increasing, most likely because of oral sex.
Herpes infections are incurable but treatable.
“Cold sore” herpes is spread easily, especially in childhood, when infected saliva is shared, such as through nonsexual kissing among family members.
Genital herpes, which is spread by sexual contact, also is common. In addition, it is costly — a 2002 study estimated that HSV-2 infections cost $1.8 billion to treat in 2000. That study also projected that as many as 39 percent of American men and 49 percent of American women could be infected with genital herpes by 2025.
Herpes is often asymptomatic, and many infected people don’t realize they have it. Symptoms include blisters that become painful open sores that heal slowly.
Genital herpes can be deadly for newborns, and women with active herpes usually have Caesarean-section births to prevent transmission to their babies.
Genital herpes also can increase susceptibility to HIV, the virus that causes AIDS.
A herpes vaccine for uninfected women is in the human trial stage, and studies show that condoms can reduce the risk of transmission.
In their new study, Dr. Xu and her colleagues reviewed data from the National Health and Nutrition Examination Surveys (NHANES), which collected blood samples from thousands of people ages 14 to 49.
The 1988-94 NHANES showed that 21 percent of 9,165 persons had HSV-2 genital herpes. This fell to 17 percent among the 11,508 persons in the 1999-2004 NHANES. The greatest decline in infections — 5.8 percent to 1.6 percent — was among teens.
HSV-1 infections also fell, possibly because of better living conditions and hygiene. However, the prevalence of HSV-1 genital infections rose from 0.4 percent to 1.8 percent.