The public health workforce tasked with fighting what has long been a lost battle against sexually transmitted infections now faces a new, unfamiliar prospect: hope.

After rising to record levels virtually every year this century, overall diagnoses of the three most important bacterial STIs have increased since the Covid pandemic. From 2022 to 2023, total diagnoses fell 2 percent to 2.46 million new cases, according to a surveillance report from the Centers for Disease Control and Prevention. published on Tuesday.

And importantly, diagnoses of primary and secondary syphilis – the most infectious stages of the infection – fell by 10% last year to 53,000 cases.

The decline was driven by a 13% drop in such syphilis diagnoses among gay and bisexual men, who are about 2% of the adult population, but historically accounted for almost half of such cases.

STIs also spread disproportionately among young people and racial minorities. Just under half of the top three bacterial STIs were diagnosed among 15- to 24-year-olds last year. Almost a third of the cases were among blacks, who make up 13% of the population.

Overall, gonorrhea decreased by 7%, to 601,300 cases, last year; which followed a 9% decline the previous year. Among all stages of syphilis, cases increased by 1%, to 209,250 diagnoses. Chlamydia remained stable from 2021 to 2023 at about 1.65 million cases.

“I think we’re at an inflection point, and it’s important to move forward and take advantage of future STI prevention innovations and investments,” said Dr. Laura Bachmann, medical director of the CDC’s Division of STI Prevention.

The six other infectious disease experts who spoke to NBC News about the CDC report said they thought the sudden shift in syphilis diagnoses among gay and bisexual men could be an early signal of those men’s eager adoption of a new, proven protocol in which the oral antibiotic doxycycline is used to prevent STIs.

“This is a huge cause for celebration. And I’m a little surprised that we’re already seeing this trend nationally,” said Dr. Julie Dombrowski, a professor of medicine at the University of Washington.

Referring to a recent drop in syphilis among men in Seattle, she added, “We’ve definitely seen it locally.”

Some experts have expressed hope that doxycycline use among gay and bisexual men will have a positive spillover effect on women of childbearing age.

Syphilis poses the greatest threat to newborns, among which it can cause severe birth defects and death. While STI cases in newborns have increased by 30% annually in the last years — extremely alarming public health experts — the upward trend has slowed. Such promising change was apparently driven in part by nationwide efforts to increase testing among pregnant women.

In another hopeful development, a shortage that started in early 2023 of the only recommended treatment for syphilis among pregnant women, Pfizer’s Bicillin-LA, decreased.

In recent years, a trio of randomized controlled trials showed that instructing gay and bisexual men and transgender women to take a 200-milligram doxycycline tablet within 72 hours of condomless sex reduced chlamydia and syphilis among them by more than 70% and gonorrhea by about 50% %.

The the protocol is known as doxyPEPwhich is short for post-exposure prophylaxis with doxycycline.

The San Francisco Department of Public Health was the first to recommend doxyPEP for gay and bisexual men and trans women, in October 2022. CDC followed suit in June. So do health departments in other big cities, such as Chicago and new yorkwhere the LGBTQ community health centers they started giving doxycycline in patients.

A study of doxyPEP among cisgender women in Africa failed to show effectiveness. There is, however, a process in progress in US women.

Thanks to penicillin, the nation made steady progress in fighting syphilis after World War II. In the mid-1990s, public health leaders entertained the possibility that STIs could be eliminated.

But the approval of effective HIV treatment in 1996 reduced public fear of AIDS. That helped trigger a long decline in condom use especially among gay and bisexual men. Subsequent approval of the HIV prevention pill — called pre-exposure prophylaxis, or PrEP — in 2012 only accelerated the decline.

Bacterial STIs have increased accordingly.

DoxyPEP offers a promising form of harm reduction. It is inexpensive and well tolerated, and can be easily integrated into the routines of many gay and bisexual men receiving prescriptions to treat or prevent HIV.

Early analysis suggests doxyPEP is a hit for that population.

A published study This month, the journal Sexually Transmitted Diseases found that San Francisco’s contraceptive guidelines were linked to a drop in STIs among local men. A published study in next month’s issue of the magazine found that of about 900 gay and bisexual men recruited for a survey via hookup apps, half had heard of doxyPEP and nearly all expressed interest.

A spokesperson for PrEP-focused telehealth service MISTR told NBC News that since the company began offering doxyPEP in April, three-quarters of users who have filled PrEP prescriptions since then have also requested and received doxycycline. (The representative declined to provide the number of users it assumed, but said MISTR serves “more than 450,000 patients in all 50 states, DC and Puerto Rico.”) Since then, the overall quarterly STI positivity rate in among MISTR users decreased from 12. % to 6%.

In November 2023, the Food and Drug Administration approved the first tests at home for gonorrhea and chlamydia, which public health experts hope could also help fight the spread of STIs.

And in July, researchers findings presented at a global HIV conference in Munich, where gay and bisexual men in Canada and female sex workers in Japan were instructed to take 100 milligrams of doxycycline daily. The protocol, called doxyPrEPgenerally demonstrated comparable efficacy in preventing STIs compared to doxyPEP trials among gay men.

Research is ongoing to address concerns that the increased use of doxycycline to prevent STIs may be contributing to the growing supply. the crisis of drug-resistant pathogens. So far, researchers have found reassuring signs.

STI prevention experts are also concerned that, as with HIV PrEP, doxyPEP will prove disproportionately popular among whites and therefore only spread. racial disparities in STI transmission. Research is underway to look at trends in the use of doxyPEP, which could help focus promotion of the intervention where the need is greatest.

Public health experts have attributed this century’s rise in STIs, at least in part, to a constant funding of state and local public health clinics.

Dr. Jeffrey Klausner, an infectious disease expert at the University of Southern California, who led the first study to demonstrate the effectiveness of doxyPEP, required renewal of STI care spending.

“If Trump is going to make IVF — in vitro fertilization — free,” Klausner said of the president-elect. emphatic campaign commitment“they should make STI testing and treatment free.”