Syphilis, gonorrhea, and chlamydia are catching on with more and more people, says the Centers for Disease Control (CDC).

Rates of these sexually-transmitted diseases (STDs) are on the rise, the CDC warns in a recent report. Both the number of infections per capita and the total number of cases for all three STDs have been steadily rising since the 2000s. All in all, the report adds, infection rates are at their highest level since the CDC began keeping track of chlamydia cases in 1984.

A social endeavor

The CDC says that the increase isn’t automatically attributable to a bump in the number of infected individuals. As testing becomes more commonplace, each state naturally reports higher numbers of positive results. The observed increase, the CDC explains, can be caused by more states reporting on cases of these three STDs, or by them improving testing practices.

Still, the recent increases from year to year, when testing practices have not dramatically changed, likely indicate an increase in the number of infections themselves, the authors note.

For chlamydia, they report, increased testing and the refinement of testing methods (the report notes to the expanded use of “nucleic acid amplification tests” between 2000 and 2011 in particular) likely drive most of the observed increase in cases. This view is further reported by a separate CDC document that found no statistically significant increase in the chlamydia rate between 1999 and 2012.

That being said, the current report does note that the current prevalence of chlamydia is “surprising”, especially among young, sexually-active women. Around 4% of women aged 15 to 24 tested positive for the disease, compared to 1% of men in the same age group and under 1% for both men and women in other age groups. Chlamydia is generally asymptomatic in women, the report notes, meaning that many then act as unwitting carriers of the disease to male partners.

Syphilis and gonorrhea are less common, the report notes. However, both have seen recent rises in prevalence, after falling to historic lows in the early 2000s. Gonorrhea infections in particular increased by 82.6% since reaching a historic low in 2009. The CDC suggested that “multiple factors” are at play, including “drug use, poverty, stigma, and unstable housing, which can reduce access to STD prevention and care,” “decreased condom use among vulnerable groups,” and “cuts to STD programs at the state and local level.”

Both increases seem to be primarily driven by “men who have sex with men” (MSM, a stated-sexual-preference-neutral term used by the CDC and other public health organizations). MSM accounted for the majority of primary and secondary syphilis diagnoses since at least 2014, the report adds. By 2015, MSMs were 24 more likely to have gonorrhea than women, and 31 times more likely than “men who have sex with women.” In a companion release, the CDC suggested that “multiple factors, including individual behaviors and sexual network characteristics,” may determine the high prevalence of STDs among MSM. Those network characteristics included “high prevalence of STDs, interconnectedness and concurrency of sex partners, and possibly limited access to healthcare,” as well as socioeconomic disadvantage among certain MSM subpopulations.

One of the most heartbreaking findings from the study is a dramatic increase in syphilis cases among newborns (congenital syphilis); the reported number of such cases nearly tripled since 2014 to 1,306 cases in 2018.

Antibiotic-resistant gonorrhea is also featured in the report. The CDC explains that over half of such infections reported in 2018 were resistant to at least one antibiotic. However, the centers also explain that ceftriaxone, the ‘first line of defense against gonorrhea’, remains effective at its intended role.

The full report “Sexually transmitted diseases Surveillance 2018” is available here.