Syphilis is climbing in wealthy countries that thought they had left it behind, and in Japan the drug that cures it is running out. The Japanese Society for Sexually Transmitted Infections has told doctors to prioritize what penicillin remains for pregnant women, after Japanese medical societies announced that shipments of a long-acting treatment are about to stop.

The pattern spans continents, and it amounts to a full-scale syphilis outbreak. The Kirby Institute at UNSW Sydney reported this week that syphilis and gonorrhoea rates in Australia have risen more than 50 percent over the past decade, with nearly 6,000 syphilis diagnoses recorded in 2025. In Japan, doctors logged 7,700 syphilis cases in the first eight months of 2026, on top of more than 13,000 cases last year. And the World Health Organization warned in July that the world is off track on its 2030 targets for sexually transmitted infections, which it said are probably getting worse.

An old infection, a new curve

Syphilis used to be a footnote in rich-country clinics. In Japan, annual cases hovered between 500 and 900 from 2000 to 2012. Then the curve bent upward: 7,983 cases in 2021, 13,228 in 2022, and a peak of nearly 15,000 in 2023. Officials in Tokyo attribute the rise to how easily people meet strangers through apps and dating sites, combined with a reluctance to talk about STDs and a steady supply of misinformation.

Australia is seeing the same pattern. Most syphilis diagnoses are in men, but infections among women have grown 167 percent over the past decade compared with 39 percent among men, according to the Kirby Institute. That shift matters because syphilis in pregnancy can be catastrophic. There were 14 congenital syphilis cases in Australia in 2025, part of 113 cases over a decade in which 40 infants died. The country declared syphilis a communicable disease incident of national significance in 2025.

There is one bright spot in the Australian data. Among gay and bisexual men, new syphilis diagnoses have fallen 30 to 37 percent over the past three years, and researchers link the decline to wider use of doxycycline post-exposure prophylaxis, an antibiotic taken after sex that prevents syphilis and chlamydia. The pill, known as doxy-PEP, does not work as well against gonorrhoea, so condoms and regular testing are still the recommended defenses there.

The cure is getting scarce

Penicillin remains the standard treatment for syphilis, and it is the only drug recommended for stopping transmission from mother to child. That is why a supply failure in Japan is so worrying. According to a report this week from ArokaGO, Japanese medical societies announced that shipments of the long-acting benzathine penicillin product Stelues would stop once manufacturer inventories run out, prompting the call to ration supplies for pregnant women.

The shortage traces back to two failures. Pfizer voluntarily recalled its syphilis treatment in July 2025 after foreign matter was found in the product, and a manufacturing equipment failure followed that November. The company now expects shipments to resume in the second half of 2027, after facility preparations and regulatory checks are complete. Until then, Japanese doctors are left managing a stubborn epidemic alongside a dwindling supply of the one drug that ends it.

What this means for you

The global picture is equally uncomfortable for a syphilis outbreak of this size. WHO's mid-term report on its 2022-2030 strategies says more than a million cases of four curable STIs occur each day, while resistance to ceftriaxone, the main treatment for gonorrhoea, has passed 5 percent in several countries. "This report tells two stories," WHO Director-General Dr Tedros Adhanom Ghebreyesus said in a statement. "It demonstrates what is possible when countries invest in health, communities and science. But it also shows how quickly progress can be undone."

The practical advice has not changed, but it has become more urgent. Many STIs have no symptoms, so regular testing is the only reliable way to know your status. Australia's updated guidelines recommend at least three syphilis tests during pregnancy. Ask a GP or sexual health clinic about doxy-PEP if you are at higher risk, and use condoms. If a partner tells you they have tested positive, have the conversation about testing and treatment that healthy relationships require, and get treated yourself, because untreated syphilis can cause infertility, miscarriage and stillbirth. Syphilis is entirely curable when treatment is available. Keeping it that way is now a public-health fight.