A new study from the University of Washington Schools of Public Health and Medicine estimates the viral loads below which the herpes simplex virus-2 is unlikely to be transmitted. The study was conducted with the Fred Hutchinson Cancer Research Center in Seattle and published in the Journal of the Royal Society. Mathematical models were used since it is impossible to directly measure genital viral load at the time of sexual activity. Researchers predicted that transmission is unlikely at viral loads of less than 10,000 copies of herpes simplex virus (HSV)-2 DNA. Antiviral therapies or immunotherapies that maintain viral load below that level could prevent most if not all transmissions.