My friend AJ, a 31-year-old artist who lives in Brooklyn, told me about a guy he's seeing: "Every time we tried to have sex, he would lose his erection as soon as the condom went on," he explained. "After three or four times, he told me that he'd been on PrEP almost two years and had become so used to sex without a condom that he couldn't keep an erection with one on."

"That's not the only reason I stopped seeing him,” explained AJ, who is negative and not on PrEP. "But it didn't help."

Welcome to modern gay dating, when a divide is growing between gay men who are on PrEP and those who aren't. That divide, in turn, has lead to a divide between gay men who use condoms and those who don’t. It's perhaps the biggest condom divide since the early 1980s, before it was definitively proven that HIV was spread through anal sex and that condoms could prevent transmission.

As someone who's been HIV-positive and undetectable for 16 years, I'm shocked by the number of PrEP users I've met who are barebacking. Don't get me wrong—I've certainly enjoyed it. With them on PrEP and me being undetectable, we're doubly protected against HIV. And, let's face it, sex without condoms just feels better. (HIV-positive guys gave up using condoms with other poz men long ago.)

But the part of me that came of age in the 1980s can't escape the concern that we as a community are courting disaster again. Here in New York, negative guys still using condoms can feel like they're being discriminated against. "I've found myself increasingly shut out of the sexual landscape,” says another friend, Manuel. "We've already got Grindr and the apps transforming gay interactions, and now there's PrEP. I feel like the world is moving on without me, but I don't want to get on that boat."

Manuel says he finds himself shying away from guys on PrEP even before they tell him their condom policy. "Their sexual policies are out of sync with mine."

In the wake of the big international AIDS conference in South Africa last week, new research suggests a few things about this phenomenon:

1. There is yet more proof that HIV-positive people with undetectable viral loads are virtually incapable of transmitting the virus. One study didn't find a single transmission among some 50,000 sexual acts between both hetero and gay couples.

2. PrEP use in the U.S. has skyrocketed but the majority of gay men on it are still older, white and concentrated in gay meccas like New York and San Francisco. That's despite the fact that the highest rates of HIV remain among young men of color.

3. A large study in France and Canada found that taking PrEP even just four times a week (versus daily) is highly effective in preventing HIV. But it also found that once participants knew for sure that they were on PrEP and not a placebo, their amount of bareback sex rose dramatically.

It's no surprise that rates of syphilis, gonorrhea, chlamydia and other STDs have exploded among gay men. (One survey showed that, of the 434,456 sexually transmitted infections reported last year, 54,275 were among men who have sex with men, a 10% increase since 2014.)

A friend who works in a clinic with a large gay client base says his office is a virtual STD-treatment mill. In fact, they regularly run out of antibiotics to treat all the cases they see. For me, this has eerie echoes of Randy Shilts' portrait of pre-AIDS New York in And the Band Played On.

"If there's that much bareback sex going on," he asks, "who's to say that a super-drug-resistant syphilis or gonorrhea isn't evolving? Or that we're not right around a corner from a new deadly virus we don't know about yet?”

He has a point: HIV circulated in the gay world for years before symptoms finally emerged, and guidelines about Zika transmission via sexual contact are constantly being updated.

Another positive friend just received a painful penicillin shot to treat his syphilis. (Spoiler: it wasn’t in his arm.) Still, he maintains, "I think sex was meant to be enjoyed without condoms." He's barely seen a condom in three years—with positive or negative guys.

Of course some gay men say the pleasure of unprotected sex just isn't worth the risk. "I’m not really keen on going on long-term medication just to bareback," says Doug, a producer in L.A. who is HIV-negative. "That doesn’t have enough value to me."

But Doug is 47, and this condom divide is partly generational: "I'm a '90s kid who was raised to be terrified of HIV/AIDS," says Ruben, 31.

Ruben had bareback sex on PrEP but is now off it and looking to "open up" his current relationship to other partners.

"Even before PrEP," he says, "I saw all my poz friends living normal healthy lives by taking just one pill a day, which made HIV lose its scare factor for me. PrEP even more so. Getting STDs made me reconsider bareback sex, but only briefly. To be honest, I just can't see myself using condoms anymore."

All of which leaves me feeling deeply conflicted: On the one hand, I love seeing gay men, young and old, feeling this freedom and sex-positivity after decades of equating intimacy with disease and death. But, even though there's no evidence we're facing wholly untreatable STDs or are on the cusp of a new microbe with the lethality of HIV, I do worry.

Are we creating the perfect sexual landscape for lightning-fast transmission?