This Week in Sex is a weekly summary of news and research related to sexual behavior, sexuality education, contraception, STIs, and more.

Aussie Study: Condom Use Goes Down When PrEP Use Increases

Pre-exposure prophylaxis (PrEP) has changed the meaning of safe sex—at least as it relates to HIV risk.

Taken by people who are HIV negative but considered at high risk for infection (such as gay men with multiple partners), this pill-a-day regimen is 90 percent effective if taken correctly. While this is excellent news in the fight against the HIV pandemic, public health experts have worried that it will cut down on condom use and therefore make users more susceptible to other sexually transmitted infections (STIs). Now, a new study published in the Lancet shows there may be reason for these concerns.

Between 2013 and 2017, researchers at the University of New South Wales in Sydney, Australia, surveyed almost 17,000 men who said they had recently had casual sex with a male partner. The percentage of HIV-negative men who were taking PrEP rose steadily from 2 percent when the study began to 24 percent at the end. And HIV did, in fact, decline in the region.

At the same time, however, the percentage of men who said they used condoms consistently fell from 46 percent to 31 percent. And this change in behavior seemed to affect men who were not taking PrEP as well; sex without a condom increased 9 percent among this group.

Martin Holt, the lead researcher on the study, told the New York Times, “It’s great that these guys are feeling optimistic about avoiding HIV, but it has disrupted prevention methods at the community level.” The fear is that with lower condom rates, HIV rates will drop but the rates of other STIs—such as chlamydia, gonorrhea, herpes, and syphilis—will go up. While these STIs are often thought of as less serious than HIV, there are long-term health consequences associated with each of them.

This study did not measure rates of STIs in New South Wales, but rates of these infections are rising in various U.S. populations, including men who have sex with men and infants infected congenitally. Dr. Paul Volberding, the director of the AIDS Research Institute at the University of California, San Francisco, asked rhetorically, “Does this mean that pushing PrEP is a bad thing? Of course not. It is preventing HIV which is what it was designed to do. But the challenges posed are no minor issue, and we need to take them seriously.”

HIV can be prevented through use of PrEP, and vaccines can prevent Hepatitis B and human papillomavirus (HPV), the virus that causes genital warts and cervical cancer. But other than abstinence, condoms remain the only form of prevention against our most common STIs.

Japanese Condom Maker Already Preparing for the 2020 Tokyo Olympics

Many records were set at the Olympic Games in Pyeongchang, South Korea, earlier this year. but we here at This Week in Sex only care about one—the unprecedented 110,000 free condoms distributed to athletes. The tradition of distributing condoms to athletes might not date back to the original Greek Games, but it has been a staple of Olympic villages in recent years. And at least some condom companies have been getting ready for the 2020 Tokyo games for longer than some of the athletes who will compete.

“When Tokyo was selected to host the 2020 Olympics, condom distribution at the athlete village immediately came to our minds,” Hiroshi Yamashita, senior manager and spokesperson at Japanese condom maker Sagami Rubber Industries, told French news agency AFP. “The company worked hard to get the 0.01mm products to market well before the Tokyo Olympics.”

Yamashita is referring to the company’s thinnest condom, which is made out of polyurethane, and was introduced in 2013. Rival manufacturer Okamoto Industries introduced one of the same thickness in 2015. Tomonori Hayashi, a marketing manager for Okamoto, explained, “Condoms are an effective means to help people protect themselves from contracting sexually transmitted diseases, and the thinner they are, the more men tend to use them.”

In general, polyurethane condoms are thinner than the more popular latex condoms and conduct heat better. Those qualities make sex with this type of condom feel more like, well, sex without a condom, while still providing STI and pregnancy prevention. But there’s a downside: Polyurethane condoms are not as stretchy as their latex peers and can break more easily. And because they are newer, there is less research about how well they prevent STIs.

Japanese condom companies are not known global household names like industry giants Trojan and Durex, and condom sales in the country have slowed down since 2000 as the country’s population ages and other contraceptive methods have become more available.

Both companies see the Olympics as an international marketing opportunity. Yamashita told AFP: “We see [the Tokyo Games] as an extremely precious opportunity to let the world know about Japan’s high-technology.”

Luckily for them, figure skater and condom connoisseur/critic Adam Rippon—who told his Instagram followers that the condoms handed out in Pyeongchang were “generic“—won’t be competing in the summer games in Tokyo.

Sex Can Kill You, If You’re an Antechinus

Two species of marsupials, the black-tailed and silver-headed antechinus, were just discovered in Australia in 2013. A few years later, the tiny mouse-like creatures may be on the verge of extinction due to the male’s biological reaction to sex.

During their two-week mating periods, the males try to have sex with as many females as possible while also fending off potential rivals for female attention. They have marathon sex sessions, sometimes lasting as long as 14 hours. These epic sex binges leave the male exhausted, but that’s not what ultimately kills him. The excessive production of testosterone required for all this screwing and sparring causes the body to keep producing a stress hormone that actually destroys their organs.

Andrew Baker, a mammalogist at Queensland University of Technology, compared the dying males to zombies: “They’re honestly like the walking dead towards the end,” he said. “I’ve seen them stumbling around during the day—they are nocturnal mostly—still looking for mates, bleeding from various parts of their body and their hair has fallen out.”

Females live for two years, during which time they have between six and 14 babies. Males only live for about a year.

All of this makes us thankful we’re humans. There’s no such thing as too much sex, and it rarely kills us (except in bad movies where the cheating man dies on top of his mistress). On the plus side, antechinuses sure do make the most of their short lives.