risks for hsv-1 transmission by asymptomatic shedding

[tech1024]

Hi,

I am HSV-1 positive by antibody test and am not sure if it is oral or genital because I don't have any clear memory of outbreaks in either area over the past 15 years.  I was in a monogamous relationship with a woman for 15 years who had genital herpes but did not know if it was HSV-1 or HSV-2. She also had no outbreaks over that 15 year period, but had a few confirmed outbreaks prior to our relationship.

Now I am involved in a relationship with a new woman and am very concerned about transmitting HSV-1 to this new partner either orally or genitally.  Since I have no symptoms I am concerned about my own asymptomatic shedding of the virus.  My question is what the possibilities are of any of the following:

1. Giving my new partner oral HSV-1 through kissing

2. Giving her genital HSV-1 through my oral contact with her genitals

3. Giving her genital HSV-1 through vaginal intercourse with a condom

4. Giving her oral HSV-1 through her oral contact with my genitals

I don't know the HSV-1 status of this new partner, but would assume it's negative as she has no memory of any cold sore ever.

One final question is whether the presence of asymptomatic shedding automatically means transmission of the virus through skin to skin contact, such as oral sex?  Or is the chance of transmission based on the chance of shedding combined with the chance of the skin contact actually spreading the virus?

Thank you for any help you might give.

[Edward W Hook, MD]

Welcome to the Forum,  I will do my best to address your questions.  In doing so however, let me remind you that these are probabilities that we’ll be reviewing and that if something only happens once in a million times but you are the one, then the odds don’t mean much.  For this reason I suggest that you discuss your concerns with your partner.  I also suggest that she get tested.  The odds are that, like you, she has HSV-1 but does not know it.

1& 2. The answer to these questions is pretty much the same.  If your new partner does not have HSV-1 the chances of transmitting infection are low.  Things in your favor are that you have never had known outbreaks.  Odds are your infection is oral in location but you cannot be sure.  Wherever your infection is, you probably do have some asymptomatic shedding of virus.  On the other hand, most exposures to asymptomatic shedding do not lead to infection.
3.  Condom protected sex.  Chances are your infection is oral making genital transmission unlikely. Condom protection would further move things in your favor, against transmitting infection to her.
3.  Oral contact with your genitals. Very, very low risk.

Hope this helps.  EWH

[tech1024]

Thank you for this information. I have one *final* question because I am taking this condition seriously and want to make sure my understanding is clear.

Viral shedding is necessary in order for transmission to occur because it is the mechanism by which virus reaches the skin surface.  If there is no shedding then there is no risk of transmission by skin contact.

This implies that if there is a 1% chance of transmission by sexual contact with someone who has asymptomatic shedding, and there is a 5% chance of that person actually having shedding at the time of contact, then the total risk of transmission for that single sexual contact would be .01 x .05 = .0005

I understand that these numbers are estimates and that in reality they exist as statistical ranges with variance for the individual, but am I understanding the underlying principal of the transmission risk correctly?

Thank you again for your patience and for the incredibly valuable service you are providing this online community.

[Edward W Hook, MD]

Good questions.

1.  Asymptomatic shedding is a fact and is the source of the majority of tranmission of herpes infections to others.  HOWEVER, most exposures to infected partners who are shedding do not lead to transmission.  In fact we believe that less than 1% of contacts to persons with asymptomatc shedding lead to transmission of infection.  The principle here is the same as the fact that you have no doubt been around people with colds but did not get them.  You are correct about the lack of research.  it would be impossible to appropriately directly study this issue.

2.  Antiviral therapy such as valacyclovir does reduce asymptomatic shedding and transmission of HSV-2.  it has not been studied for HSV-1.  In general, due to biological variablity of the two types of virus, it takes higher doses of therapy to impact HSV-1 shedding than it does for HSV-2..

As I said, the first step for you is to have yoru partner tested.  Let's hold further questions until at least then.  EWH

[Edward W Hook, MD]

Your estimates are correct and in the right ball park for unprotected sex with an infected partner.  If you do not know your partner's status or are using condoms as is recommended, the risk is even lower.  This will end this thread.  No further questions please.  EWH

[tech1024]

Dr. Hook, Thank you for your fast and complete reply.  I have 2 additional questions I hope you might clarify for me.  And again, thank you so much for your help.

1. In answer to my original questions 1&2 you wrote that "...most exposures to asymptomatic shedding do not lead to infection".  I had originally thought that when looking at asymptomatic shedding frequencies from the latest medical literature that the shedding frequency was equivalent to the probability of transmitting the infection.  

If I understand your answer, you are saying that the presence of asymptomatic shedding during sexual contact does not automatically mean a transmission to my partner.  It means a higher risk, but not a guarantee of transmission.  Is that correct?  I assume no current research details the probable risks of transmission during asymptomatic shedding but if any exists I would greatly appreciate any links to such research.

2. I have read that taking 5 days of Valacyclovir has a clinically proven reduction in asymptomatic shedding.  Is that correct, and if so, do you know if it applies to oral shedding as well as genital shedding?  I am particularly concerned about giving my partner genital HSV-1 from my (probably) oral HSV-1 infection through oral to genital contact.

Thank you again.