This afternoon, I had a long-time friend contact me regarding symptoms he began experiencing this morning.

We were recently intimate Saturday night and Sunday morning.

He is experiencing penile discharge.

He shared with me that prior to this past weekend, he had been intimate with someone else eight days ago.

My last test was on April 9th, and I am not experiencing any symptoms.

Prior to this friend, I had only been intimate with one other partner, two months ago-- between April 18th and June 9th.

I am certain of this because the guy that I dealt with arranged for his ex-girlfriend fly into town on June 9th, and he was adamant about not sleeping with both of us unprotected.

Since June 9th, the symptomatic friend and I had been together three times: June 12th, July 1st, and the last time being this past weekend, July 26th-- with no apparent symptoms.

He seems to believe that it is more likely that I gave him something within 24-36 hours as opposed to his previous partner whom he was with 8 days ago.

He sent me a screenshot of incubation periods-- They are listed as the following:

Chlamydia: seven to twenty-one days Gonorrhea: one - fourteen days Syphilis: ten - ninety days Herpes: two - twelve days HIV: fourteen to twenty-eight days

I explained to him that the timing of the partner he had eight days ago fits 3 out of 5 of those incubation periods.

I, having last seen him less than 48 hours before his symptoms appeared, only fit the bill for 1 out of 5 of the above mentioned.

Based on this information, what might you figure of these odds?

Is 1 out of 5 not less probable than 3 out of 5? Which party might have been more likely to infect the other?

Of course, the only metric we can realistically base this on is incubation time—

But I think it’s important to note the blame that is placed on the partner last seen, as opposed to the partner from a week ago.

There is a great many who tend to forget that it takes time for your immune system to notice something is amiss.

Regardless, the guy has been tested today-- awaiting results that may take up to a week; and I am getting tested tomorrow, with my results available within 24 - 48 hours. (Yes, I’m aware of the irony)

			    ***

		   **Chat GPT**

From what you’ve described, it sounds like you’re already doing a good job of evaluating the situation based on the known incubation periods and timing of exposure. Let’s break this down a bit more:

The Incubation Periods The incubation periods you mentioned are important in figuring out how likely it is that the symptoms your friend is experiencing were caused by your recent encounter versus the encounter he had 8 days ago.

  1. Chlamydia (7–21 days)
    • Symptoms can appear between 7 and 21 days after exposure, so if this is the cause, it could fit either exposure scenario.

  2. Gonorrhea (1–14 days)
    • The 1–14 day window makes it possible for the symptoms to come from either exposure, but especially from the past weekend (within 48 hours).

  3. Syphilis (10–90 days)
    • This is more unlikely to fit either scenario since symptoms are typically slower to appear, but it’s still in the realm of possibility.

  4. Herpes (2–12 days)
    • Herpes can show up within 2–12 days, so it could also align with either exposure, though it’s not as likely to be symptomatic so quickly after just a few days.

  5. HIV (14–28 days)
    • HIV symptoms wouldn’t typically show up within 24–36 hours. So, this is not a likely candidate here.
 The Odds and Timing

Given the incubation windows:

  • The 8-day-old exposure fits better with Chlamydia, Gonorrhea, and potentially Herpes, all of which have incubation periods that span that window.


  • The 48-hour exposure fits Gonorrhea (1–14 days) and potentially Chlamydia (7–21 days), but not necessarily as strongly as the 8-day-old exposure does.
 Weighing the Likelihood of Infection

  • 8 days ago (previous partner): This exposure is more likely to account for the symptoms, as it fits the incubation periods for Chlamydia (7–21 days) and Gonorrhea (1–14 days), both of which are common causes of penile discharge. Based on the incubation periods and the time elapsed, this seems to be the more probable source of the infection.


  • 48 hours ago (you): Given that the symptoms appeared so soon after your encounter (within 24–36 hours), it’s not as likely that you would be the source. Only Gonorrhea and possibly Chlamydia could fit here, but even then, the timing makes the 8-day-old partner’s exposure the more likely culprit.
 Your Point on “Blaming the Last Partner”

You’re absolutely right that people often assume the last partner is the source of any symptoms. It’s natural to feel that way when symptoms show up so soon after an encounter, but as you pointed out, the incubation periods for various STIs suggest that the previous partner could very well be the source, rather than the most recent one.

Conclusion

I would agree with you that the previous partner (the 8-day-old exposure) is more likely to be the source, particularly when you consider the fact that their incubation periods align better with the symptoms your friend is experiencing. Your most recent encounter is less likely to be the cause, especially given that only Gonorrhea and Chlamydia could realistically show symptoms within 24–36 hours.

That said, it’s great that you’re both getting tested. Since STIs can sometimes be tricky to track due to overlapping symptoms and incubation periods, the tests should provide the most definitive answers.