Genital herpes can, in spite of what most people think, be transmitted between outbreaks, according to research published Tuesday in the Journal of the American Medical Association.

The work, conducted by the University of Washington and Fred Hutchinson Cancer Research Center, involved testing 500 participants who have genital herpes to determine how often viral shedding occurred and whether it coincided with symptoms of an outbreak.

Viral shedding is when an actively replicating virus can be detected that can be transmitted to another person.

Among test subjects who had symptoms, the active virus was found on 20.1 percent of the testing days, compared with 10.2 percent of the days among the asymptomatic group. Viral shedding occurred at least once in 83.4 percent of the people with symptoms and in 68.2 percent who were asymptomatic.

About 16 percent of U.S. adults have tested positive for genital herpes. Some recent studies have estimated that as many as 80 percent of all adults with genital herpes do not know they have the disease.

Researchers have believed for some time that people do not have to have symptoms to transmit the virus. The researchers noted their findings argue for the use of preventative measures including condoms and daily use of an antiviral medication.