[Question #5280] Oral to genital HSV-1 transmission risk (MSM)

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76 months ago
I’m having some difficulty navigation all the data and research on HSV-1 transmission.

I hope you can give me some clarity on the probability of transmission of HSV-1 from a seropositive male to a seronegative male via oral sex. 

I realize there is a lack of MSM-specific research, but I am assuming the risk can be inferred from oral-to-genital data in female (positive) to male (negative) transmission of HSV-1. My understanding is the risk is as low as 4% per year.

A secondary question would be whether suppressive therapy using valcyclovir, in a MSM discordant relationship where one partner has HSV-1 and another partner does not have HSV-1, would be statistically significant in prevention of the negative partner acquiring HSV-1 genitally. My understanding is suppressive therapy decreases the risk by roughly 50%.

Would you recommend that a discordant couple utilize suppressive therapy to minimize the risk of transmitting HSV-1 from the seropositive partner to the seronegative partner?

Any details you can provide on the probability of transmission would be appreciated. The seropositive partner has not had any symptomatic recurrences of oral HSV-1 since the the assumed primary infection 15+ months ago.

Thank you for your time and expertise.
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Terri Warren, RN, Nurse Practitioner
76 months ago
We don't have data on transmission of HSV 1 to someone else, unfortunately.  We only have transmission data on HSV 2. 
My suggestion would be first to clarify that actual status of the person believed to be negative.  If an IgG test is negative (and I can't tell from your post if that has been done) it is important to know that the IgG test misses 30% of HSV 1 infections, compared to the gold standard herpes western blot.  Whether the person believed to be uninfected wants to do that is certainly optional.  If the person wants to assume they are negative then the infected person could take daily antiviral therapy to reduce the risk of transmission, yes, certainly.  AGain, we have no data on the efficacy of antiviral therapy in reducing transmission of HSV 1 - for HSV 2 it is around 50%, yes. 

Terri
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