The high rate of herpes infection is a clear indication that herpes is particularly contagious. Of the two strains of the herpes simplex virus, herpes simplex 1 and herpes simplex 2, herpes simplex 1 is thought to infect ninety percent of adults, and herpes simplex 2 is thought to infect twenty percent of adults. Herpes simplex is most contagious during a symptom outbreak, however research has indicated that the herpes simplex virus can be at the skin surface, and can thus be transmitted, even when an outbreak is not occurring as a result of viral shedding. Herpes is spread through skin-to-skin contact.