Since 2003, the number of sexually transmitted infections (STIs) in the U.S. rose a staggering 90% in what has been called an out-of-control epidemic. However, the most recent national data from 2023 indicates the first signs that those STIs trends may be slowing.
Gonorrhea dropped for the second year in a row, declining by 7% from 2022 and dipping below pre-pandemic levels when rates increased after the initial stay-at-home orders were lifted. Meanwhile, overall syphilis cases increased by only 1% after years of double-digit increases, according to the Centers for Disease Control and Prevention (CDC). Primary and secondary syphilis cases dropped 10% from 2022, and newborn syphilis increased by 3% after increasing by an alarming 30% in prior years. The rates of chlamydia remained about the same in 2023 as the year prior.
In a statement, Dr. Jonathan Mermin, the director of CDC's National Center for HIV, Viral Hepatitis, STD and TB Prevention said he saw a “glimmer of hope amidst millions of STIs.”
"After nearly two decades of STI increases, the tide is turning,” Mermin said. “We must make the most of this moment — let's further this momentum with creative innovation and further investment in STI prevention."
Millions of STIs still occurred in 2023, and experts warn that it will be essential to continue funding public health prevention programs and potentially expanding access to treatments like DoxyPep if the nation is to see these trends persist. STIs are still shrouded in stigma and many people do not seek care or don’t have access to care.
“There is a lot of concern that we may have had a small step forward but are facing further reductions," said Dr. Jeffrey Klausner, who studies STIs at the University of Southern California. “You get the public health you pay for, and if you don’t pay for it, you’re going to have bad sexual and reproductive health outcomes.”
"It's not ever one thing right that causes either an epidemic or causes things to slow down."
There are likely multiple factors that played a role in reducing the spread of STIs: Public health departments used funding issued as part of the COVID-19 pandemic, expanded testing in nontraditional settings like emergency rooms or churches, and funded a workforce of disease intervention specialists who perform contact tracing and connect people to treatment.
Meanwhile, sexual behaviors among men who have sex with men are thought to have changed as a result of the mpox outbreak in 2022, and the CDC began officially recommending the antibiotic doxycycline (doxy PEP) — which works like a “morning after pill” for STIs — to this community, along with transgender women.
“It's not ever one thing right that causes either an epidemic or causes things to slow down,” said Dr. Ina Park, a professor of Family Community Medicine at the University of California, San Francisco. “It's a concerted effort on multiple fronts.”
Untreated STIs can lead to infertility and increase the risk for cervical and anal cancers. Congenital syphilis, in which syphilis is transmitted to an infant, can lead to miscarriages, stillbirth or disabilities.
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In recent years, the 30% increase in congenital syphilis has alarmed doctors and public health officials. This STI is easily treatable with a shot of penicillin during pregnancy, and a CDC report found that almost 90% of cases in 2022 were preventable.
The National Syphilis and Congenital Syphilis Syndemic Federal Task Force ramped up educational outreach, prevention services, and surveillance. This helped public health departments understand where outbreaks were occurring and find the communities that needed the outreach most, said Dr. Oni Blackstock, founder and executive director of Health Justice, a racial and health equity consulting firm.
“In response to this congenital syphilis epidemic, there was a national coordinated response to increase access to syphilis testing for pregnant people, for cisgender men who have sex with men, and for people who are involved in sex work,” Blackstock told Salon in a phone interview. “A number of efforts were put forward to get people diagnosed early and get people connected and treated with penicillin as soon as they were diagnosed.”
However, inequities persist among people of color. For example, American Indian and Alaska Natives represented 0.7% of births in 2023, but accounted for 4.6% of congenital syphilis cases. Black Americans were also disproportionately affected, along with people in the South compared to other regions in the U.S.
“STIs follow social disparities in the United States,” said David Harvey, the executive director of the coalition of STD directors. “Communities of color, women and young people all bear a disproportionate number of STIs, so we know that it takes special efforts to reach those communities.”
In June 2024, the CDC officially recommended doxy PEP for men who have sex with men and transgender women to treat syphilis, chlamydia or gonorrhea. However, many health departments had already started offering doxy PEP due to the overwhelmingly positive response it showed in clinical trials, reducing chlamydia and gonorrhea by 70% and 50%, respectively.
Although there have been some concerns raised about antibiotic resistance and the use of this medicine, doxy PEP was associated with a 50% decline in chlamydia and syphilis in men who have sex with men and transgender women in San Francisco in a study published earlier this month in JAMA Internal Medicine. In the national 2023 data, there was a 13% decline in primary and secondary syphilis among men who have sex with men.
“We suspect that in San Francisco, doxy PEP has had an effect on men who have sex with men and trans women,” said Dr. Oliver Bacon, a senior supervising physician at San Francisco City Clinic, which is run by the local health department. “Declines in San Francisco and other declines nationwide are probably multifactorial, and it’s hard to pinpoint one cause.”
Although men who have sex with men and transgender women experience some of the highest risk for STIs, there have been efforts to test whether doxy PEP could work to treat STIs in people assigned female at birth as well. However, in a trial published late 2023 in the New England Journal of Medicine, many of the participants who were assigned to take doxy PEP didn’t actually take it, which may have affected the null results, said Dr. Connie Celum, a professor of global health and medicine at the University of Washington.
“If you look at the pharmacologic data the CDC generated and presented about a year ago, the levels of doxycycline in vaginal secretions is almost identical to the rectal and blood plasma, meaning it should work in women,” Celum told Salon in a phone interview. “Adherence was likely a big part of why it didn’t work.”
This year, a federally-funded study will be launched to test the effect of doxy PEP in people assigned female at birth, so more data should be forthcoming. Researchers have emphasized the need for this community to be included in these trials so they are not left behind.
Cisgender women, and particularly young cisgender women, have high rates of chlamydia, which tends to be asymptomatic in this population and is usually detected through screening, Blackstock said.
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"Doxy PEP has been shown to be effective in cisgender men who have sex with men and trans women, and we don’t yet have the data to support its use in cisgender women, a group that if shown to be effective could benefit greatly from this STI prevention strategy," Blackstock said.
Many are hopeful STIs will continue to decline so long as there is an investment in STI prevention and surveillance resources. However, funding for STI programs has remained relatively flat, and departments are having to stretch the same funds to handle far more cases. There was a one-time allocation of $1.2 billion stemming from COVID legislation dedicated to STI prevention, but $400 million of that was rescinded under debt ceiling legislation.
“Our history as a field has been: not enough resources, some small increases granted by the U.S. Congress in the last few years, and a one time infusion of money that was then rescinded,” Harvey said. “All of this adds up to a very difficult scenario around expanding our response in the U.S. commensurate with the scope of this problem.”
Studies consistently show that more public health funding to prevent STIs leads to a reduction in cases. In one study, each $1 increase in per capita federal STI and HIV prevention funding was associated with a 21% decrease in gonorrhea. Another found each $0.10 in federal funding spent to eliminate syphilis was associated with a 28% reduction in cases.
“We have some tools to prevent STIs and bend the curve down on the STI epidemic,” Bacon said. “It’s really: Do we as a society commit the resources to doing that at scale?”
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