Herpes simplex virus infections are transmitted through contact with infected oral or genital secretions. The virus can be present on mucosa during a symptomatic recurrence or asymptomatically. Most transmissions to neonates and sexual partners occur during asymptomatic viral shedding. The frequency of viral isolation in the absence of lesions ranges from 2% to 6% of days; however, studies using more sensitive tests, such as polymerase chain reaction, show that viral shedding can occur on the average 28% of days.