The rise of STIs in Australia, and how we can curb it

Sexually transmitted infections are a growing public-health concern in Australia. The Kirby Institute’s annual surveillance shows syphilis, gonorrhoea and chlamydia all climbing: syphilis diagnoses have tripled over the past decade, gonorrhoea has more than doubled, and chlamydia has risen too. Here’s what’s behind the rise in the three most common bacterial STIs, and how regular testing helps turn it around.

Chlamydia

Chlamydia remains the most commonly reported STI in Australia, with 94,184 notifications in 2025, most among people aged 20 to 29. Chlamydia has fluctuated over the past decade and slightly declined over the past year, but the gap between notifications and the number of Medicare-rebated tests suggests many cases still go undiagnosed. Rates among Aboriginal and Torres Strait Islander peoples are around 2.5 times those of non-Indigenous people.

It’s a bacterial infection spread through vaginal, oral and anal sex, and it can affect the cervix, urethra, testicles, throat, anus and eyes. Because it usually causes no symptoms, the only way to know is a chlamydia test. It’s easily cured with antibiotics, but left untreated it can cause pelvic inflammatory disease and infertility, and can pass to a baby at birth. See our guide to the long-term risks of chlamydia.

Gonorrhoea

Gonorrhoea has climbed even faster, with 42,393 notifications in 2025 — part of a rise of more than 50% in the diagnosis rate over the past decade. Rates are higher among men, particularly men who have sex with men (men made up 73% of gonorrhoea diagnoses in 2025), and around four times higher among Aboriginal and Torres Strait Islander peoples.

It’s also bacterial, and can affect the genitals, rectum and throat. Symptoms differ between men and women and are often absent altogether, which helps it spread. Left untreated it can lead to PID and, rarely, serious infections of the heart (endocarditis) and brain (meningitis). A gonorrhoea test is the only way to confirm it — and if you’re not sure how it differs from chlamydia, see chlamydia vs gonorrhoea.

Syphilis

Infectious syphilis has surged over the past decade, with the diagnosis rate up more than 50% and 5,986 diagnoses in 2025. Most diagnoses are still among men (78% in 2025), but the steepest rise has been among women — up 167% over the decade, compared with 39% among men. Rates in Aboriginal and Torres Strait Islander communities are around six times higher than in non-Indigenous populations. Worryingly, congenital syphilis — passed from mother to baby in pregnancy or at birth — continues, with 14 cases in 2025 and 40 infant deaths recorded over the past decade.

Syphilis is a bacterial infection with four stages, and is best treated early. It begins with one or more painless sores, and its symptoms change over time; if untreated it can eventually damage the heart, brain, spinal cord, eyes and bones, and in severe cases can be fatal. A syphilis test detects it in its early stages, when it’s easily cured.

Why are STI rates increasing?

There’s no single cause. Contributing factors include:

• changing sexual behaviours
• less condom use, partly as HIV pre-exposure prophylaxis (PrEP) has become widely available
• lower awareness of STIs and the value of regular testing
• stigma, which stops people seeking advice and treatment.

The COVID-19 pandemic also reduced testing and access to services, which affected the data from 2020 to 2022.

How regular testing reduces STI rates

One of the best ways to bring rates down is regular STI testing, so anyone with an infection is treated promptly. Because many STIs have no symptoms, testing is often the only way to know. If you test positive, telling recent partners so they can be tested matters too; if that’s hard, an anonymous SMS can do it, and a Specialist GP can help. Always finish the full course of any antibiotics, and re-test afterwards to confirm the infection has cleared.

Testing is the single most effective lever we have as individuals. Anyone who’s sexually active benefits from a routine check, and it’s worth testing sooner after a new partner, unprotected sex, a condom mishap, or any symptoms. A full screen covers chlamydia, gonorrhoea, syphilis, HIV and hepatitis B in one go, so a single test gives you a clear picture.