One Partner Undetectable, One on Prep, HIV Risk?

[MascTop]

I don’t know if I’m being overly paranoid, but I will explain what happened. So about a two weeks ago, I topped a guy I recently started hooking up with. I’m positive/undetectable for over 10 years. Last VL test was last month, undetectable. The guy who bottomed for me is on Prep and has been for months. 
 

I topped him two nights in a row. About 10 days later, he came down with a mild fever for two days and felt better after. That freaked me out. I know ANYTHING can cause a fever but the timeline is what is spooking me. 
 

Given that I am fully undetectable and he is on prep… are there any odds that I could have infected him? If anyone can share any insight, I would so appreciate it. 

[Slut4anyload]

Chance is zero if you really are undetectable, whether or not he is actually on PrEP.

[viking8x6]

The odds are so small that they literally cannot be measured. For all practical purposes the chance of infection in that situation is zero.

 

[PozBearWI]

@MascTop no need for you to freak out.  

[norefusal]

most infections come w fevers. this could be anything from a bug bite to hiv from someone else. either way, this is what dr. visits r for:  likely answers and suggested solutions. 

but if he's on prep he's probably getting regularly tested so the truth will out soon enough. 

either way, if you're U it's highly unlikely u infected him. long story short: you're acting responsibly: taking your meds and breeding guys who say they r on prep. anything more seems like belts and suspenders to me. 

[MascTop]

On 9/2/2025 at 10:26 AM, viking8x6 said:

The odds are so small that they literally cannot be measured. For all practical purposes the chance of infection in that situation is zero.

 

Thank you. Do you happen to know anything about the risk of viral spikes/blips and how that could affect being undetectable? I was fully UD on my last test (below 20 copies), which was within two weeks of these encounters. Just wondering if that’s something I should be concerned about. I’ve been fully adherent to my ARV as far as I remember.

 

[viking8x6]

24 minutes ago, MascTop said:

Thank you. Do you happen to know anything about the risk of viral spikes/blips and how that could affect being undetectable? I was fully UD on my last test (below 20 copies), which was within two weeks of these encounters. Just wondering if that’s something I should be concerned about. I’ve been fully adherent to my ARV as far as I remember.

 

Short answer: No, it's not something you should be concerned about!

Long answer: First, the other guy is on PrEP, which means that even if he were fucking someone with a viral load, he'd be OK. Second, the studies that proved that undetectable=untransmissable didn't test people every day or week, so those statistics included the risk of viral blips - and the conclusion was that U=U even if the partner was not using protection. Third, @norefusal is right - you are already doing everything that you should be, and a mild fever is a common symptom of just about any virus that produces symptoms at all.

[PozBearWI]

43 minutes ago, MascTop said:

Thank you. Do you happen to know anything about the risk of viral spikes/blips and how that could affect being undetectable? I was fully UD on my last test (below 20 copies), which was within two weeks of these encounters. Just wondering if that’s something I should be concerned about. I’ve been fully adherent to my ARV as far as I remember.

 

The basis of u=u were the partner studies, done 15 to 20 years ago when we could only measure down to 200 copies.  At that level of viral load there were no partner to partner infections for serodiscordant partners that weren't show to be from the positive partner.  As long as you're below 200; even if you are above 20 please don't fret it.  Viral blips while common still fall within the <200 metric.  When they don't that indicates that the individual is in treatment failure and alternative ARV's will be tried.  

[MascTop]

35 minutes ago, viking8x6 said:

Short answer: No, it's not something you should be concerned about!

Long answer: First, the other guy is on PrEP, which means that even if he were fucking someone with a viral load, he'd be OK. Second, the studies that proved that undetectable=untransmissable didn't test people every day or week, so those statistics included the risk of viral blips - and the conclusion was that U=U even if the partner was not using protection. Third, @norefusal is right - you are already doing everything that you should be, and a mild fever is a common symptom of just about any virus that produces symptoms at all. 

20 minutes ago, PozBearWI said:

The basis of u=u were the partner studies, done 15 to 20 years ago when we could only measure down to 200 copies.  At that level of viral load there were no partner to partner infections for serodiscordant partners that weren't show to be from the positive partner.  As long as you're below 200; even if you are above 20 please don't fret it.  Viral blips while common still fall within the <200 metric.  When they don't that indicates that the individual is in treatment failure and alternative ARV's will be tried.  

Thank you both so much for those insights. I’m trying to weed out any and all possibilities. Or as my therapist would probably say- “catastrophizing the situation”