Doctors are commonly asked how to keep from spreading genital herpes from one partner who has it, to another who doesn’t, even without lesions.
Asymptomatic (no sores) shedding of Herpes Simplex Virus (HSV) is known to occur. This means you can transmit HSV without having actual sores on your genitals—but you can take action to prevent transmission.
Let me start out by saying three important things:
- Condoms are the best way to prevent transmission.
- If you have an active sore on your genitals, don’t have sex until it clears.
- Most of what we know comes from studies on folks with HSV type 2 (HSV-2) so we assume it’s the same as with HSV-1 but there is no science behind that yet.
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Here are the main things to know about reducing the risk of transmitting HSV from an infected person to a non-infected partner:
- Suppressive therapy with a valacyclovir 500 mg pill once daily is beneficial in decreasing transmission to an uninfected sexual partner.
- How do we know that? In 2004, a large study published in NEJM (New England Journal of Medicine) studied 1484 heterosexual couples: one partner had HSV-2 infection and the other didn’t. The HSV infected people took either 500 mg of valacyclovir once daily or nothing (placebo) for eight months.
- The susceptible partner (the partner who had never had genital lesions from HSV) was evaluated monthly for clinical signs and symptoms of genital herpes.
- Taking valacyclovir 500 mg daily led to a reduction in transmission of genital HSV-2 to the uninfected partner.
- What are the chances I’ll get HSV from “asymptomatic shedding” from my partner? After 8 months of being sexually active with a partner who has asymptomatic HSV infection, 16 of 741 (3.6%) who didn’t take valacyclovir developed an outbreak of herpes—compared to only 4 of 743 (1.9%) in those whose partners were taking valacyclovir 500 mg daily.
- Valacyclovir 500 mg taken daily reduces to almost zero the days when HSV-2 DNA is detected in genital secretions, which is why it helps prevent transmission.
- Does it matter if the genital ulcers are from HSV-1 or HSV-2? Remember, valacyclovir has not been studied in those with genital lesions due to HSV-1 though we assume the reduction in risk is similar. Half of new cases of genital lesions are caused by HSV-1 so the old idea that HSV-1 is the mouth and HSV-2 is the genitals no longer applies.
- Is valacyclovir better than acyclovir or famciclovir? The three appear to have the same effectiveness for suppression of repeat HSV infections, yet only valacyclovir has the evidence listed above—where it has been shown to limit spread from infected person to non-infected person
Hope this helps.
Once-daily valacyclovir to reduce the risk of transmission of genital herpes.N Engl J Med. 2004 Jan 1;350(1):11-20.