There is lots of evidence to say that reducing the HIV viral load will reduce the chance of HIV passing. What they are currently trying to work out is how much it reduces the risk. Most of the research to date has been done on heterosexual couples so it has mainly looked at the reduction in risk from vaginal sex.
Currently there are two ongoing studies which have also included same sex male partners to see what the risk is from anal sex.
I have cut a pasted some information from an article we have titled “Insight into HIV transmission risk when the viral load is undetectable and no condom is used” just click on the link to view the entire article.
Risk over time
Upper confidence limits were also calculated for a couple’s 10-year risk of HIV transmission when the HIV-positive partner has an undetectable viral load:
• Receptive vaginal sex (with or without ejaculation) – 11.7%
• Insertive vaginal sex – 11.4%
• Receptive anal sex (with or without ejaculation) – 17.9%
• Insertive anal sex – 12.8%
For example, the upper confidence limit for receptive anal sex can be interpreted as follows:
Given that couples were having condomless sex about once a week, it is extremely likely that the 10-year risk of HIV transmission is somewhere between 0 and 17.9% for receptive anal sex. While it is still possible that the “true” risk is zero, or only slightly higher than zero, the study could not rule out the possibility that the risk is as high as 17.9%.
It is important to note that the size of the upper confidence limit reflects the effects of chance. Receptive anal sex has the highest upper confidence limits because there were fewer receptive anal sex acts during the study compared to other types of sex. The lower number of sex acts means chance may have played a greater role.
The studies are still ongoing and as time goes on we will have a better idea of how much the risk is reduced by having an undetectable viral load.
Certain sexually transmitted infections can increase the chance of HIV passing so it is also a good idea to go for regular STI tests if there is a chance of this happening. Receiving regular HIV care is also important to be certain the viral load stays undetectable.
Also people’s situations can be different, for example how long has the person been on HIV medication and how long has their HIV viral load been undetectable. It may be helpful going with your partner to their next HIV medical appointment if they are ok with this. The health provider you see could discuss the risk to HIV while taking your partners medical history into consideration.
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