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

Number of Chlamydia Cases Remains High, Especially Among Young People

The Centers for Disease Control and Prevention (CDC) has released a new report that estimates almost two million cases of chlamydia occur each year. The estimates are based on data from the 2011-12 wave of the National Health and Nutrition Examination Survey, for which over 8,000 people were interviewed and examined by a health-care provider. The data showed that approximately 1.9 percent of people ages 14 to 39 have chlamydia. More alarmingly, 4.2 percent of sexually active young adults ages 14 to 25 have the bacterial infection.

Diagnosed cases of chlamydia have to be reported to the CDC, which documented 1.4 million cases in 2012, making it the most common reportable bacterial infection. But many cases of chlamydia go undiagnosed because for many men and women there are no symptoms. Once diagnosed, the infection can be easily cured with antibiotics. If left untreated, the infection can lead to pelvic inflammatory disease, which can in turn lead to infertility.

Chlamydia can infect the throat, genitals, or anus. The survey estimates, however, only looked at genital infections because the study determined whether a participant had chlamydia using a urine sample; to find chlamydia in the throat or anus, it is necessary to do a culture. If all sites of infection were included, it stands to reason that the estimates would be higher.

The researchers involved in this study noted that given the high prevalence of the disease, the low cost of the test, and the high cost of treating chlamydia infections that go undetected, routine screening (which is now recommended for all sexually active young women ages 24 and younger) is cost-effective.

Virus Returns in Second Baby Thought Cured of HIV

A new case study in The Lancet provides more evidence that antiretroviral therapy (ART) cannot eradicate HIV from a baby’s body, even if given shortly after birth, as had previously been hoped.

As Rewire reported this summer, the first baby thought to have been born with, but then “cured” of, HIV was found to once again have detectable levels of the virus in her blood. The case got a lot of attention earlier in the year when doctors announced that the child, known as the Mississippi baby, was virus-free despite having been off of her ART for over five months.

The case was unusual—the baby’s mother, who was HIV-positive, received no prenatal care and as such did not get the drug therapy that could have prevented mother-to-child transmission. Once doctors realized the newborn was also HIV-positive, they gave her high doses of ART and then put her on a continuing regimen. But the child was no longer brought to the clinic between 18 and 23 months of age; during that time, she was not given her medicine. When she returned to the clinic, her physicians were surprised to find that she was nonetheless free of detectable virus and began to suggest that giving ART right after birth may have “cured” her.

Based on this case, the National Institutes of Health planned to launch a global study to see if they could replicate the results by giving HIV-positive infants standard antiretroviral drugs immediately after birth, and doctors around the world began to consider this protocol. Doctors at a hospital in Milan, Italy, for example decided to stop giving ART to an HIV-positive 3-year old because he had an undetectable viral load and had been given high doses of ART just four days after his birth in 2009. Doctors hoped that the drugs had “cured” him of HIV and that he didn’t need to continue taking them.

Unfortunately, that was not the case. Professor Mario Clerici, of the University of Milan and the Don Gnocchi Foundation in Italy, noted in a case report recently published that just two weeks after ART was stopped, tests revealed that the virus had returned. The researchers concluded that the Italy and Mississippi baby cases show that while “antiretroviral drugs are effective in reducing HIV morbidity and mortality, they are ineffective in eliminating viral reservoirs so are unable to eradicate HIV.”

However, these cases serve as a good reminder that when pregnant women receive prenatal care and those who are HIV-positive are put on ART during pregnancy, it is possible to prevent mother-to-child transmission in the first place.

Less Pubic Hair, Fewer Critters?

A new study adds to the mounting evidence that our society’s current preference for pubic hairlessness has at least one benefit: fewer cases of pubic lice. The study—Pubic Lice; An Endangered Species?—looked at the cases of pubic lice at a hospital in a small city outside of London between 2003 and 2013. It found that infestations fell from 1.8 percent of patients to 0.07 percent during that time. Moreover, 94 percent of the patients who did have pubic lice (sometimes referred to as crabs because of what they look like under a microscope) had not shaved, waxed, or otherwise altered their pubic hair.

For the study, researchers also surveyed a random sample of clinic patients and found that during the ten-year period the proportion of people who reported total pubic hair removal increased from 19 percent to 31 percent, and the proportion who removed some of their pubic hair jumped from 23 percent to 56 percent. The survey found that hair removal was much more common among women than men—68 percent of female respondents took it all off, compared to 30 percent of males. Though still not proof of cause and effect, the researcher pointed out that new crab infections in 2003 were relatively evenly divided between women (53 percent) and men (47 percent), but in 2013 far more of the cases were in men (82 percent) than women (18 percent).

In her article on the study for Wired, Gwen Pearson suggests another explanation for fewer cases of lice: the spread of information. She notes that “a quick check of Google searches related to pubic lice (aggregated via algorithm) shows a slight decline in searches from 2004-2014, but not the dramatic decline one might expect from the infection data reported in these papers.” So perhaps it’s not that people aren’t getting crabs as much as it is that they are self-diagnosing and self-treating.

Pearson also notes that pubic hair grooming is a phenomenon that mainly occurs among the wealthy and the white, both because of cultural expectations and because of the costs involved in trying to fight Mother Nature. Furthermore, while the incidence of pubic lice may be shrinking in one population, that does not mean that the organism is marching toward extinction.