Casually mention that you're going for your semi-annual 10 panel, bait their views out.

If they look clueless or ask what that is? Easy response, "Complete STI panel, with results in 3-5 days to your account to share with partners. PP, university/college sexual clinics and your own family doctor only test for 5 harmful STI's that cause permanent damage, so this is a more complete check-up on top of basic testing."

If they know what it is or get the idea? Feel it out further. "Yeah, imagine my surprise after ___ years of testing that Herpes is never included when you say "test for everything". Apparently a waste of funding when it's not an STI, and most adults have already been exposed and have no symptoms."

You'll be able to tell whether they seem offended that you MIGHT be implying they have it and not know, or something like that. In that case? Why bother, ditch them.

If they give off the vibe that they know how common it is and it's really not a big deal, or might even have it themselves and were considering broaching the subject themselves? Go ahead, disclose.