Developments in Brief : Herpes: Half of All Adults May Have It

People who are infected with genital herpes but show no outward signs of the disease can still pass it on to their sexual partners, and this may be a common way in which the ailment is transmitted, researchers report.

Experts now believe that perhaps as many as half of all adult Americans already have the disease, but most of them don’t know it.

Dr. Stephen E. Straus and colleagues at the National Institute of Allergy and Infectious Diseases provide clear evidence of one case in which a man with no rash or blisters gave genital herpes to a woman during a single sexual encounter.

Physicians have long suspected that this can happen. The new report, published in the New England Journal of Medicine, shows that they were right.

New studies indicate that perhaps two-thirds to three-quarters of people with genital herpes infections don’t know they have it.