Incidence and Transmission
Current estimates indicate that more than 100 million Americans have oral herpes, and at least 50 million (1 in 5 people over age 12) have genital herpes (Workowski et al., 2010). Worldwide genital herpes cases number in the hundreds of millions, and 24-25 million people are newly infected each year (Looker et al., 2008). Genital herpes infections in the United States are more common in women than in men, which may indicate that male-to-female transmission is more likely than female-to-male transmission (Centers for Disease Control, 2009f).
Genital herpes appears to be transmitted primarily by penile-vaginal, oral-genital, genital-anal, or oral-anal contact. Oral herpes can be transmitted by kissing or through oral-genital contact. A person who receives oral sex from a partner who has herpes in the mouth region can develop either type 1 or type 2 genital herpes.
When any herpes sores are present, the infected person is highly contagious. It is extremely important to avoid bringing the lesions into contact with someone else’s body through touching, sexual interaction, or kissing.
Although it was once believed that herpes could be transmitted only when lesions were present, we now know that HSV can be transmitted even when there are no symptoms (Workowski et al., 2010). In fact, research strongly indicates that asymptomatic "viral shedding" (the emission of viable HSV onto body surfaces) is likely to occur at least some of the time in many people infected with HSV (Tronstein et al., 2011; Worcester, 2012). This asymptomatic viral shedding can result in transmission of the virus despite the absence of symptoms that suggest active infection. Many people who are infected with HSV are unaware of their infection, and the majority of infections are transmitted by these individuals (Mark et al., 2008).
Research has shown that herpes viruses do not pass through latex condoms. Thus condoms are effective in preventing transmission from a male whose only lesions occur on the glans or shaft of the penis. Condoms are helpful but less effective in preventing transmission from a female to a male, because vaginal secretions containing the virus can wash over the male’s scrotal area. Nevertheless, using condoms consistently and correctly can minimize the risk of either acquiring or transmitting genital herpes.
What can infected people do to reduce the risk that they will transmit the virus to a sexual partner? Clearly, when lesions are present, individuals should avoid any kind of intimate or sexual activity that will expose a partner’s body to viral shedding of HSV. However, as previously described, even when no sores or other symptoms are present, infected individuals are at risk for shedding the virus. The best strategy for people who are either infected themselves or involved with an infected partner is to consistently and correctly use condoms even when they or their partners are asymptomatic.