Transmission risk ratio calculated

[Adam]

So, I’ve been looking at the research for risk ratio of transmitting HSV2 to try to get numbers of the risk involved with a new healthy partner. I would love your feedback on it. I’ve cited my sources at the bottom.

 

According to the biggest (as far as I know) study conducted, by Dr Wald, the risk of transmitting HSV during each single sex act without a condom is 0,09%. If you (the carrier of HSV2) do not have HSV1, the risk is 2,34 times less = 0,04%. If you use a condom, the risk is 0,08% of that = 0,003%. According to the study by Corey, taking Valaciclovir regularly will reduce the risk of transmission another 48%, taking us down to 0,0016%.

 

There are other factors that you can include if you know which specific partner you are assessing, (race, age, partner HSV1 status etc) , but for making a generic calculation, I have left those out. (I do not have HSV1, which is why included that, but that can be taken out if you are uncertain of your own status)

 

I also have not been able to include other suppressive factors such as using anti-viral condoms (with viva-gel) or taking L-lysine (makes outbreaks and thus active transfer less common, but no study proves it to reduce transmission from shedding), since there are no transmission studies on them.

 

Would you agree that this is correct, or have I missed something?

 

Since this is calculated per act, naturally risk will increase with time (approx. x10 per year if having sex twice a week). I’ve chosen to focus on the first act/s with a new partner, since that is when “the talk” should be had. Knowing that it is per act, it is up to both partners to decide how to deal with the risk continuously.

 

Condom use and transmission of herpes, Dr Wald, University of Washington, Seattle

https://pdfs.semanticscholar.org/26c9/466e5038d074d3564b8aa5bbe5bdeeea625c.pdf

Antiviral suppresive therapy

https://www.ncbi.nlm.nih.gov/pubmed/15319087

 

[optimist]

> Would you agree that this is correct, or have I missed something?

 

Not really, no. I don't think it's possible to pinpoint a "per act" risk because too many variables exist. I'll use my own case as an example...

 

Asymptomatic female with long established HSV2 infection who takes daily antivirals. Average shedding rate for someone like me without antivirals is 10% (37/365 days), but with antivirals is 2.5% (9/365 days). So let's imagine I have sex every single day of the year (which is 3x more often than the risk studies account for). I pose 0% risk during 356 of 365 sex acts. Roughly speaking, if I have sex all 9 days I'm shedding, that represents perhaps a maximum collective risk of 3% (condoms) or 6% (no condoms). That's not precisely how it works when having sex 3x as often, but close enough. And even if you then say the risk is less than 1% per each of those 9 acts, that's still not entirely accurate because risk varies on each of those days. I suppose I could say in my individual circumstances that risk is zero percent 97.5% of the time and up to 3% (condoms) or 6% (no condoms) 2.5% of the time and I just don't know when those 2.5% of times are occurring.

[Adam]

Thanks @optimist for your reply, much appreciated.

 

It is of course true that you can never know when that one time of the ratio is occuring, it could be the first time or the 1000th or more time. I realize the reality is trickier to determine, but I'm still interested in looking at the ratio.

 

According to your statistics, the risk would be 0,075% (0,025x0,03), for transmitting when having sex with a condom one time at a random occasion.

 

Your numbers are new to me, e.g. that a condom would only protect twice as much as not having one? Where are you getting your numbers from? Could you link me to those/that study? Thanks.

[RegularGuy]

I would advise against holding too closely to the statistics. The fact of the matter is that contact with the virus results in infection.

It is enough to disclose before getting intimate and be ready to demonstrate patience and understanding while the other person weights out how they feel about the situation. The statistics are helpful in allowing another person to understand the situation, but they are by no means an accurate representation of how their life will turn out individually.

The important point of the statistics is to demonstrate that there are steps that can be taken to help prevent transmission, but to also assert that there are no guarantees.

It is meant to encourage those who are H+ to be responsible, take preventative measures, and to disclose in order to get real consent from their partners. Then, to help the other person understand that there is a way to gauge whether the H+ person they are interested is already doing everything they can to prevent putting them at risk.

[Adam]

Hi RegularGuy, thanks for your feedback.

 

I agree that statistics are by no means the full picture and that we who are H+ have full responsibility to disclose our status and gain consent without pressure from a new potential partner before engaging in sexual activities.

 

However, like you also point out, statistics are helpful in allowing the other person understand the risk and the situation, and when doing that I want to make sure I have the correct statistics to give them, based on research and sound logic.

 

We are all different in what approach feels best for us. It is indeed always important with compassion and patience, but as a logic driven and academic person if I was on the receiving end of such a conversation, I would feel more comfortable if the person telling me had their facts straight, showing that they were serious enough about their research to have read up on it properly. I do not think it is “enough to disclose before getting intimate”, that disclosure could very well lead to a discussion in which I want to be prepared. By just saying there is a risk, without being able to assess that risk, it could just as well be 1/10 as 1/100,000, and I would not feel that I had taken as much responsibility as I should have if I could not be more precise. I believe knowing the facts and their sources adds a great deal of trustworthiness in this kind of talk. With the correct information at hand, and knowing that it is just statistics, not a guaranteed reality in the individual case, it is up to the other person to decide how they feel about that risk and the situation as a whole.

 

This is why I’m trying to find out in this thread whether these statistics are correct or if there are additional studies or sources that I should take into consideration.

 

[optimist]

I still think it's misleading to describe risk per sex act. I'll provide a different example to explain what I mean, again using the stats I quoted earlier that apply to an asymptomatic woman with HSV2 who takes daily antivirals. On average, someone with this profile is shedding virus 2.5% of the time. Sometimes it's enough to potentially infect someone if multiple factors come together, sometimes the level of shedding is too low to infect someone or other factors come into play that increase or reduce risk on the partner's side.

 

So let's say I'm this woman and I have sex (with a condom) with a different partner every day of the year. 365 partners and none of them have HSV2. I met them at all a HSV-free pride convention. Because I'm shedding virus 2.5% of the time, 9 of the partners were potentially exposed to the virus, 356 were not exposed. You asked about condoms and the reason I say 9 were still exposed is because shedding occurs from the genital tract and these partners are likely coming into skin-skin contact with my vulva and perineal area if we're having vaginal sex. Condoms are believed to reduce female to male risk by roughly 50%. They're more effective in reducing male to female risk (I believe closer to 90% though I don't know the exact number) because more of the shedding area is covered by the condom. In other words, transmission risk is significantly higher male to female when no condoms are used but condoms provide greater benefit in reducing male to female transmission.

 

But back to my example, you can see the risk was not .0000something for each of these sex partners. The risk was zero for 356 of them, but then the risk fluctuated for the other 9 of them based on a variety of factors. In the studies of partners having sex for a year, these people were not having continuous sex with others who had a steady stream of risk. The average frequency of sex was something like 2x per week which means they were likely not even making contact on a majority of the days the partner was shedding virus.

 

 

 

[Adam]

Hi again, @optimist. Thanks for replying. I value your feedback.

 

I hear you. You are saying that you don’t know which factors are playing in at any given moment, and thus at any time the actual risk might be higher than the average risk ratio.

I fully agree, sometimes it is enough to have sex once and expose the partner that only time, if all the factors happen to coincide on that very occasion (which is why it is so important to have the talk before getting intimate the first time). Even if the risk is 1/100,000, that one time could be the first time, that’s inherent to risk/probability theory. The more times you have sex, the greater the risk is that one of those times happen to be at a time when you will expose someone. But since we can't tell when we are shedding etc., as far as we know the likelihood of that happening is equal each time. Even if the risk accumulates with the number of occasions, why do you think it is misleading to calculate the risk ratio for a single act, like they have done in the study?

 

Couples have sex with different frequency. Referring to transmission ratio for an average couple who have sex twice a week will give a skewed risk perspective for a more sexually active couple. If you break down the same numbers per sex act, you can give a more accurate accumulated risk assessment.

 

Thanks for letting me know your reasoning behind the condom. I’m a straight male, which is why I used the risk reduction ration for male -> female. It sounds like we have the similar statistics for that. Could you share what your sources are? E.g. the one about how much antivirals impact, and where did you get the info about shedding and the 6% risk (without condom) then?

 

[optimist]

@Adam The 6% was my estimate based on my scenario of having *daily* sex which is 3x more frequent than the frequency of sex in the study that states 2% per year female to male with antivirals but no condoms. It is not a perfect calculation but my goal was to provide an estimate based on a person being exposed to virus 3x more often than accounted for in the study. I wanted to explain that the actual risk is based on those 9 shedding days, not divided by 365 days or 100-150 acts or whatever.

[optimist]

@Adam Sorry, forgot to answer your other question. Whether it's misleading would be based on a few factors. How much does the other person know about how all this works? Is this being pitched to someone who is making a choice to have sex one time only or is this a long-term partner?

 

When potential partners, including casual partners, ask me about risk, I share with them that the available statistics are based on couples who have sex a couple times a week over the course of a year. I state it this way even though I know we likely won't be having sex that mirrors how those couple have sex. But I feel it could be misleading to them to divide risk by 100 acts or 150 acts or 365 days or whatever because too many variables influence risk on any given day. Just my opinion.

[Adam]

Hi @optimist

 

The scenario I have in mind would be when having the talk with a new potential partner before having sex the first time. Hopefully that will be the first of many, but at that stage it can be hard to know where the relationship will go.

 

The idea behind this post is to find out the facts in order to be as accurate as possible when discussing it with a partner. I wouldn’t say that the general risk of having sex with someone with HSV2 is that broken down number per act. The risk ratio number for one sex act would probably only be a small part of that discussion, preceded by a talk about there being a risk in general attached to getting intimate with me and whether she was ok with that. That would include a broader talk about how it works with the mix of factors such as occasional shedding, suppressing medicine and others. If she is still interested but wants to educate herself about the risks involved, I want to know that I can answer her correctly and point to reliable sources. Hence my question in this thread about whether I had calculated it right, or missed some study or other reliable sources.

 

If she decides that our emotional connection would be worth a small risk but not an ongoing risk, that would be up to her to decide. Just as if someone who is very sexual and would want sex often in a relationship, or spontaneously regardless of access to a condom, it would be fair for them to know how the risk would increase with the number of (unprotected) acts.

 

Thank you for your opinion, I appreciate it. I think maybe we have slightly different perspectives. I understand that you don’t want to downplay the risk when communicating it, and that is not what I’m trying to do, I just want to get as close to the data as possible to make sure I am correctly informed and can tell someone else accurately depending on the situation.

 

[optimist]

@Adam I agree with you that it's good to be educated enough to answer questions accurately. Personally, I tend to just keep it to the facts of my situation when I disclose and then provide more information based on their questions. I've provided the annual risk stats for people who asked about risk, and it's funny how different people can see the same numbers very differently.

[ITguy]

What is the percentage of transmission from a male to female under the following conditions?

-Taking anti-virals sporadically. (Last full month cycle was 2 months ago)

-Used two condoms(Latex/Lambskin)

-Had signs of outbreak day after, had full outbreak 3 days later.

[Sunset]

Love the statisticians here... thank you!

[Adam]

@ITguy.

I can't give you any numbers I'm afraid, most of those specific variables aren't in the studies I've read. But my amateur opinion from what I've gathered on various websites: If you haven't taken antivirals very recently the effect doesn't linger, so that won't help you. Lambskin condoms doesn't protect against virus, so that won't add any extra protection either. If you had signs of outbreak the day after, it is quite possible it had already started the night before, so that would increase the risk significantly. I don't know if there is any statistic on how long before the first signs of an outbreak you are already contagious, but if anyone in this forum knows I would love to find out!

 

@sunset. Thanks! :)