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

Zika May Have Been Sexually Transmitted From a Woman to Her Male Partner

A new case suggests that males may be infected with the Zika virus through unprotected sex with female partners. Researchers have known for a while that men can infect their partners through penetrative sexual intercourse, but this is the first suspected case of sexual transmission from a woman.

The case involves a New York City woman who is in her early 20s and traveled to a country with high rates of the mosquito-borne virus (her name and the specific country where she traveled have not been released). The woman, who experienced stomach cramps and a headache while waiting for her flight back to New York, reported one act of sexual intercourse without a condom the day she returned from her trip. The following day, her symptoms became worse and included fever, fatigue, a rash, and tingling in her hands and feet. Two days later, she visited her primary-care provider and tests confirmed she had the Zika virus.

A few days after that (seven days after intercourse), her male partner, also in his 20s, began feeling similar symptoms. He had a rash, a fever, and also conjunctivitis (pink eye). He, too, was diagnosed with Zika. After meeting with him, public health officials in the New York City confirmed that he had not traveled out of the country nor had he been recently bit by a mosquito. This leaves sexual transmission from his partner as the most likely cause of his infection, though further tests are being done.

The Centers for Disease Control and Prevention (CDC)’s recommendations for preventing Zika have been based on the assumption that virus was spread from a male to a receptive partner. Therefore the recommendations had been that pregnant women whose male partners had traveled or lived in a place where Zika virus is spreading use condoms or abstain from sex during the pregnancy. For those couples for whom pregnancy is not an issue, the CDC recommended that men who had traveled to countries with Zika outbreaks and had symptoms of the virus, use condoms or abstain from sex for six months after their trip. It also suggested that men who traveled but don’t have symptoms use condoms for at least eight weeks.

Based on this case—the first to suggest female-to-male transmission—the CDC may extend these recommendations to couples in which a female traveled to a country with an outbreak.

More Signs of Gonorrhea’s Growing Antibiotic Resistance

Last week, the CDC released new data on gonorrhea and warned once again that the bacteria that causes this common sexually transmitted infection (STI) is becoming resistant to the antibiotics used to treat it.

There are about 350,000 cases of gonorrhea reported each year, but it is estimated that 800,000 cases really occur with many going undiagnosed and untreated. Once easily treatable with antibiotics, the bacteria Neisseria gonorrhoeae has steadily gained resistance to whole classes of antibiotics over the decades. By the 1980s, penicillin no longer worked to treat it, and in 2007 the CDC stopped recommending the use of fluoroquinolones. Now, cephalosporins are the only class of drugs that work. The recommended treatment involves a combination of ceftriaxone (an injectable cephalosporin) and azithromycin (an oral antibiotic).

Unfortunately, the data released last week—which comes from analysis of more than 5,000 samples of gonorrhea (called isolates) collected from STI clinics across the country—shows that the bacteria is developing resistance to these drugs as well. In fact, the percentage of gonorrhea isolates with decreased susceptibility to azithromycin increased more than 300 percent between 2013 and 2014 (from 0.6 percent to 2.5 percent).

Though no cases of treatment failure has been reported in the United States, this is a troubling sign of what may be coming. Dr. Gail Bolan, director of CDC’s Division of STD Prevention, said in a press release: “It is unclear how long the combination therapy of azithromycin and ceftriaxone will be effective if the increases in resistance persists. We need to push forward on multiple fronts to ensure we can continue offering successful treatment to those who need it.”

HPV-Related Cancers Up Despite Vaccine 

The CDC also released new data this month showing an increase in HPV-associated cancers between 2008 and 2012 compared with the previous five-year period. HPV or human papillomavirus is an extremely common sexually transmitted infection. In fact, HPV is so common that the CDC believes most sexually active adults will get it at some point in their lives. Many cases of HPV clear spontaneously with no medical intervention, but certain types of the virus cause cancer of the cervix, vulva, penis, anus, mouth, and neck.

The CDC’s new data suggests that an average of 38,793 HPV-associated cancers were diagnosed each year between 2008 and 2012. This is a 17 percent increase from about 33,000 each year between 2004 and 2008. This is a particularly unfortunate trend given that the newest available vaccine—Gardasil 9—can prevent the types of HPV most often linked to cancer. In fact, researchers estimated that the majority of cancers found in the recent data (about 28,000 each year) were caused by types of the virus that could be prevented by the vaccine.

Unfortunately, as Rewire has reported, the vaccine is often mired in controversy and far fewer young people have received it than get most other recommended vaccines. In 2014, only 40 percent of girls and 22 percent of boys ages 13 to 17 had received all three recommended doses of the vaccine. In comparison, nearly 80 percent of young people in this age group had received the vaccine that protects against meningitis.

In response to the newest data, Dr. Electra Paskett, co-director of the Cancer Control Research Program at the Ohio State University Comprehensive Cancer Center, told HealthDay:

In order to increase HPV vaccination rates, we must change the perception of the HPV vaccine from something that prevents a sexually transmitted disease to a vaccine that prevents cancer. Every parent should ask the question: If there was a vaccine I could give my child that would prevent them from developing six different cancers, would I give it to them? The answer would be a resounding yes—and we would have a dramatic decrease in HPV-related cancers across the globe.

Making Inroads Toward a Chlamydia Vaccine

An article published in the journal Vaccine shows that researchers have made progress with a new vaccine to prevent chlamydia. According to lead researcher David Bulir of the M. G. DeGroote Institute for Infectious Disease Research at Canada’s McMaster University, efforts to create a vaccine have been underway for decades, but this is the first formulation to show success.

In 2014, there were 1.4 million reported cases of chlamydia in the United States. While this bacterial infection can be easily treated with antibiotics, it often goes undiagnosed because many people show no symptoms. Untreated chlamydia can lead to pelvic inflammatory disease, which can leave scar tissue in the fallopian tubes or uterus and ultimately result in infertility.

The experimental vaccine was created by Canadian researchers who used pieces of the bacteria that causes chlamydia to form an antigen they called BD584. The hope was that the antigen could prompt the body’s immune system to fight the chlamydia bacteria if exposed to it.

Researchers gave BD584 to mice using a nasal spray, and then exposed them to chlamydia. The results were very promising. The mice who received the spray cleared the infection faster than the mice who did not. Moreover, the mice given the nasal spray were less likely to show symptoms of infection, such as bacterial shedding from the vagina or fluid blockages of the fallopian tubes.

There are many steps to go before this vaccine could become available. The researchers need to test it on other strains of the bacteria and in other animals before testing it in humans. And, of course, experience with the HPV vaccine shows that there’s work to be done to make sure people get vaccines that prevent STIs even after they’re invented. Nonetheless, a vaccine to prevent chlamydia would be a great victory in our ongoing fight against STIs and their health consequences, and we here at This Week in Sex are happy to end on a bit of a positive note.