HSV-2 (Sorry, I accidentally posted this in HIV Prevention)

I have a few questions regarding oral sex. I have read that if a couple where the male has HSV-2 and the female is both HSV-1 and HSV-2 negative does nothing more than avoid sexual contact during outbreaks, the female has an 8% chance of contracting HSV-2 genitally in any given year. However, if the male takes 500 mg of Valtrex daily, that percentage is reduced to about 4%. I have also read many times that contracting HSV-2 orally is somewhat rare, and that even if it is contracted, once the outbreak goes away, a second outbreak usually never occurs. And I guess this is because HSV-2 prefers the genitals instead of the mouth??? Anyway, my first question is if I take 500 mg of Valtrex daily and my girlfriend performs unprotected fellatio on me only a couple of times per month, wouldn't the chances of her contracting HSV-2 orally be something of a long shot? And I know there are plenty statistics pertaining to the likelihood of transmitting HSV-2 genitally (i.e. 8% chance to male to female transmission without suppressive therapy, 4% chance of transmission with suppressive therapy), but I haven't read about the probability of transmission of HSV-2 orally. Do studies on this topic exist? Also, if she does happen to contract HSV-2 orally, she could take Valtrex to alleviate the symptoms and shorten the length of time the outbreak would be present, correct? I've read that the recommended dose to treat oral HSV-2 is a bit different than the dose to treat genital HSV-2. What would this dose be? And how long should the oral outbreak last if Valtrex is taken immediately upon noticing the first signs of the outbreak?

[Edward W Hook, MD]

You have posted on the wrong site.   Questions about STDs other than HIV belong on the STD site.  I will do my best to answer your questions with this reply but, if you have additional questions or follow-up they must be on the STD site.  Sorry.

You have clearly studied the available information and are well informed regarding herpes.  I will clarify several of the points you made and then try to address your specific questions although, as I hope to explain, there are not clear answers to some of them.

Regarding the study you cite regarding the benefits of valacyclovir prophylaxis.  The numbers you mention are correct however, please remember that everyone in the study was also counseled to use condoms all of the time and it is clear that some did and some did not.  Using condoms, in the study however was proven to further reduce genital transmission of HSV in those who did use condoms.

There are no comparable data regarding acquisition of oral HSV-2 infections.  As you note, for reasons that are not entirely clear, HSV-2 "likes" the genital tract more than it is likely to cause oral herpes.  Thus while  less is known about oral HSV-2, we do know one can get it from oral sex and that when a person has it, they tend not have fewer recurrences (i.e. cold sores due to HSV-2) than is typical when persons have genital infection.  There are NO data on how often HSV-2 is transmitted through oral sex.

Now, on to your questions:
1.  Transmission of HSV, form any site, to any site is a "numbers game".  Thus, when one has an infected partner, most exposures do not lead to transmission and certain activities (such as taking valacyclovir prophylaxis) can reduce the frequency of transmission.  Fewer exposures, lower risk.  On the other hand, there is a certain element of luck involved here too. If your chance of transmission is 1 in 1000 and you are the 1 who gets it on their first exposure, you have bad luck.  Thus the question which is operative here is, are you (or more accurately, is your girlfriend) "feeling lucky".  The more exposures one has, the more likely they are to become infected.

2.  As I said, there are no data on the risk of oral transmission of HSV-2.

3.  If she gets HSV-2, valacyclovir should help.  Studies show that higher doses of therapy are needed to have a beneficial effect on oral HSV-1.  There are no studies on therapy of oral HSV-2.  With therapy of HSV, due to person-to-person variation, sometimes there is a bit of trial and error involved to find the best dose of medication.

4.  There are no data on the effect of therapy for oral HSV-2.  Therapy for cold sores taken as soon as they appear accelerates healing by a day or two.

I hope these answers are helpful to you.  If you have further questions, unfortunately, you will need to post them on the STD site and pay another fee.  EWH