Transmission and Prevention
Herpes is contracted through direct contact with an active lesion or body fluid of an infected person. Herpes transmission occurs between discordant partners; a person with a history of infection (HSV seropositive) can pass the virus to an HSV seronegative person. There are no documented cases of infection via an inanimate object (e.g. a towel, toilet seat, drinking vessels). To infect a new individual, HSV travels through tiny breaks in the skin or mucous membranes in the mouth or genital areas. Even microscopic abrasions on mucous membranes are sufficient to allow viral entry.
HSV asymptomatic shedding occurs at some time in most individuals infected with herpes. It can occur more than a week before or after a symptomatic recurrence in 50% of cases. Infected people that show no visible symptoms may still shed and transmit virus through their skin; asymptomatic shedding may represent the most common form of HSV-2 transmission. Asymptomatic shedding is more frequent within the first 12 months of acquiring HSV. Concurrent infection with HSV increases the frequency and duration of asymptomatic shedding. There are indications that some individuals may have much lower patterns of shedding, but evidence supporting this is not fully verified; no significant differences are seen in the frequency of asymptomatic shedding when comparing persons with 1 to 12 annual recurrences to those that have no recurrences.
Antibodies that develop following an initial infection with a type of HSV prevents reinfection with the same virus type—a person with a history of orofacial infection caused by HSV-1 cannot contract herpes whitlow or a genital infection caused by HSV-1. In a monogamous couple, a seronegative female runs a greater than 30% per year risk of contracting an HSV-1 infection from a seropositive male partner. If an oral HSV-1 infection is contracted first, seroconversion will have occurred after 6 weeks to provide protective antibodies against a future genital HSV-1 infection.
Barrier protection, such as a condom, can reduce the risk of herpes transmission in some cases.
For genital herpes, condoms are highly effective in limiting transmission of herpes simplex infection. The virus cannot pass through latex, but a condom's effectiveness is somewhat limited on a public health scale by their limited use in the community, and on an individual scale because the condom may not completely cover blisters on the penis of an infected male, or the base of the penis or testicles not covered by the condom may come into contact with free virus in vaginal fluid of an infected female. In such cases, abstinence from sexual activity or washing of the genitals after sex is recommended. The use of condoms or dental dams also limits the transmission of herpes from the genitals of one partner to the mouth of the other (or vice versa) during oral sex. When one partner has a herpes simplex infection and the other does not, the use of antiviral medication, such as valaciclovir, in conjunction with a condom, further decreases the chances of transmission to the uninfected partner. Topical microbicides which contain chemicals that directly inactivate the virus and block viral entry are currently being investigated. Vaccines for HSV are currently