It is entirely possible and common for one partner in a relationship to have herpes and the other to remain uninfected. Herpes simplex virus (HSV), including both HSV-1 (often oral) and HSV-2 (often genital), is a widespread viral infection. The presence of the virus in one partner, often called a serodiscordant relationship, does not guarantee transmission. Transmission is influenced by biological and behavioral variables, meaning exposure does not automatically result in infection. Many couples successfully manage this situation for years without the uninfected partner acquiring the virus.
The Reality of Discordant Couples
A couple can remain discordant (one partner positive, one negative) primarily because the virus is not consistently active on the skin’s surface. The herpes virus resides in nerve cells and only periodically travels to the surface, a process known as viral shedding. During the vast majority of days, the uninfected partner is not exposed to a transmissible viral load.
Most new herpes infections are transmitted by people who are unaware they have the virus because they have no symptoms or only very mild ones. Between 75% and 90% of people with genital herpes may not realize they are infected. Even without any sores, the virus can shed, and this asymptomatic shedding is responsible for the majority of transmissions. The uninfected partner’s immune system also plays a role, successfully fighting off low-level exposures.
The annual risk of transmission in heterosexual discordant couples, without protective measures, is relatively low, ranging from approximately 4% to 11%. This low rate confirms that the virus does not transmit easily. Female-to-male transmission risk is generally lower (about 4% to 5% per year), while male-to-female risk is higher (around 8% to 11% annually). This difference is thought to be due to the increased surface area of mucosal tissue exposed in women during sexual contact.
Key Factors That Influence Transmission
The specific type of HSV present is a primary variable affecting transmission risk. HSV-2, typically associated with genital herpes, transmits genitally much more frequently than genital HSV-1. Although HSV-1 is increasingly responsible for new genital infections, its genital recurrence and shedding rates are significantly lower than those of HSV-2. Consequently, a partner with genital HSV-1 has a much lower overall risk of transmission.
Transmission risk is highest during an active outbreak, when visible lesions or prodromal symptoms like tingling or itching are present. The concentration of the virus on the skin’s surface is highest then, making contact significantly more likely to result in infection. Transmission can still occur when no symptoms are visible due to asymptomatic viral shedding. Shedding episodes are most frequent in the first year after infection and gradually decrease over time.
The frequency and duration of sexual contact also influence the opportunity for transmission. The amount of virus shed varies widely, and transmission is unlikely at very low viral loads (e.g., below 10,000 viral copies). Most transmissions occur during prolonged shedding episodes with high viral copy numbers. The location of the infection also matters, as genital HSV-2 has a higher rate of asymptomatic shedding compared to HSV-1.
Practical Steps for Risk Reduction
Couples seeking to minimize transmission risk have several effective strategies, starting with suppressive antiviral medication. A partner diagnosed with genital HSV-2 can take a daily dose of an antiviral drug, such as valacyclovir, which significantly reduces viral shedding. Studies show this suppressive therapy can reduce the risk of HSV-2 transmission to a susceptible partner by about 50%.
Barrier methods, particularly latex condoms, also provide protection against transmission. Consistent and correct use of condoms reduces the risk, though they do not cover all exposed skin areas where shedding might occur. For oral sex, using a dental dam can help reduce risk if the virus is present orally. These methods are most effective when used regularly.
The most straightforward behavioral intervention involves abstaining from all sexual activity during an active outbreak. This includes avoiding skin-to-skin contact, as the area surrounding a sore can be highly contagious. Open and honest communication is also a fundamental protective step, ensuring both partners are aware of the risks and committed to consistently using prevention strategies.