[Question #13592] HIV Risk/Testing at 3 weeks?

1 months ago

15 days ago, I was at an emergency room and the man sitting in the triage chair before me was homeless, and his arm was very swollen from IV drug use. I didn't think much of this and sat in the chair after him. Shortly after, I noticed that he had a large blood stain on the back of his pants. This worried me and I checked my own pants as I sat down right after him. I was wearing grey sweatpants and did notice a small red stain (about the size of a dime) that was likely blood on the seat of my pants, although I didn't notice a stain on my underwear that were also grey so I'm not sure how much it soaked through. I am wondering if is possible for HIV to be transmitted through clothes like this. I didn't necessarily have any "open wounds" on my buttocks or back of legs, but I do have some acne back there and keratosis pilaris (chicken skin). I am unbelievably stressed about this. We just had our first baby 6 weeks ago and I'm terrified to even hold him for fear of transmitting the virus.

H. Hunter Handsfield, MD

1 months ago

Welcome to the forum. I'm happy to address these issues.

In the 40+ years of the known worldwide HIV/AIDS pandemic, nobody is believed to have acquired HIV from exposure to infected blood or body fluids in the environment, by skin contact, etc. Nobody ever is infected in health care settings, other than by injury with contaminated sharps (needles, scalpels, etc) -- and even this has been virtually unheard-of for 20+ years. Nobody is known have been infected by exposure of open wounds to infected blood or fluids. That includes exposure of acne and other skin rashes. Such things may be listed (unnecessarily) in various educational materials about HIV prevention, but they are theoretical risks only. Without unprotected sex with an infected partner, or sharing drug injection equipment, you will never get HIV.

In other words, although it is conceivable the previous chair user had HIV, that did not put you at risk in any way. From a medical/risk perspective, you do not need to be tested. On the other hand, reassurance alone is a valid reason for testing: if you're going to worry about this, lose sleep over it, etc, then by all means get tested. You can have a conclusive HIV RNA PCR test at any time (valid 11+ days after exposure) or an HIV AgAb test ("4th generation", "combo", "duo" test) 6 weeks after the event. But if you do, please do your best to stop worrying in the meantime. There is no realistic possibility you acquired HIV.

I hope these comments are reassuring. Let me know if anything isn't clear.

HHH, MD

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1 months ago

Thank you for your detailed reply Dr! This does help, although I also believe I will get tested just to be sure. As my anxiety over this is so severe, I was wondering if there was any benefit to doing a 4th Gen test at 3 weeks? Online, it says that "most" infections will be positive at 3 weeks due to P24 antigen with the 4th Gen test (I saw this in a paper from K Huynh, 2023, NIH). If true, what is "most"? 70%? 90%? If it would be me at ease at all it would be worth it for me.

H. Hunter Handsfield, MD

1 months ago

Yes, there can be substantial reassurance from a negative AgAb test at 3 weeks; by that time 80-90% of newly infected persons would be positive. But you need to wait til 4 weeks for ~98% reliability and 6 weeks for 100%. But it's really already 100% certain you didn't catch HIV -- or do you really fear you might be the first such person in the world? Really, you are no more at risk of HIV than if you sat next to an infected co-worker or friend, which probably you have done (whether or not you knew it).---

1 months ago

Hi again Dr Handsfield- I hope you're well. I just wanted to update this thread with my last follow up and tell you that I waited until 4 weeks +1 day to take a 4th gen "duo" test to be more sure of my result, and I tested negative for that today. Based on the details of my "exposure", do you think I am ok to let this go now? If it were you or one of your patients, would you get tested again? (I know you basically already answered this, sorry)

Since I have you here, I was also hoping to get some more clarification on HIV in general if you have time as I have learned a lot through this scare but also had a lot of previous beliefs challenged. For example, through reading through your forum, I was shocked to learn that even "high-risk" behaviours like unprotected sex do not always, or even usually, result in HIV. I was also surprised to learn that needle-stick injuries only result in HIV infection 0.03% of the time. Why is this? I was under the impression that an exposure to the virus into the blood stream or mucous membrane would usually always result in infection. Is HIV less transmittable than other viruses? Is it in general a "weak" virus outside of the body? Why does exposure not usually equal infection? Thanks again and Merry Christmas

H. Hunter Handsfield, MD

1 months ago

Yes, you're "good to go"; you can be certain you do not have HIV.

The answer to your closing questions is yes: HIV is a lot less easily transmitted than some other viruses. No two viruses have the same transmission possibilities. Among the easiest to transmit are measles and norovirus (the main cause of viral gastroenteritis, i.e. "stomach flu". (To become infected with either of these, all you have to do is be in the room with an infected person, breathing the air.) HIV is one of the hardest to transmit: lots of virus must have contact with certain kinds of cells which typically are deep inside the body. It has nothing to do with HIV being a "weak" virus, however. For more info you might try an AI program like ChatGPT, with a question something like "Compare the infectiousness of different viruses, such as influenza, hepatitis B virus, HIV, norovirus, measles, and cytomegalovirus." You'll see great differences. (I'm not endorsing ChatGPT in particular. It's just one possibility.)

That completes the two follow-up comments and replies included with each question and so ends this thread. I hope the discussion has been helpful. Best wishes and stay safe.

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