Sexually transmissible infections remain a significant public health issue in Australia, with new data showing syphilis and gonorrhoea rates remain high.
New sexual health data released today by the Kirby Institute at UNSW Sydney shows a mixed picture for Australia, with rates of syphilis and gonorrhoea remaining high after significant increases since 2016 - and chlamydia stable but still the most commonly notified sexually transmissible infection (STI). First Nations peoples continue to experience higher rates of all STIs, highlighting the need for sustained investment in culturally safe sexual health services.
In 2025, there were 5986 syphilis diagnoses, 42,393 gonorrhoea diagnoses and 94,184 chlamydia diagnoses. Syphilis and gonorrhoea diagnosis rates have both increased by more than 50% over the last decade, while chlamydia has fluctuated, and slightly declined over the past year.
Untreated STIs can cause pelvic inflammatory disease, infertility, and pregnancy and newborn complications, including miscarriage and stillbirth.
"These data are an important reminder that sexually transmissible infections remain a public health issue in Australia. The rise in syphilis and gonorrhoea tells us we need to ensure testing and treatment are easy to access and prevention efforts reach the people and communities most affected," says Dr Skye McGregor, an epidemiologist at the Kirby Institute at UNSW Sydney and the report's lead.
"Sexual health is a normal and important part of overall health and wellbeing. Many STIs have no symptoms, but they can be detected and treated easily, which supports both individual and community health," says Dr McGregor. "People who are sexually active can prioritise their sexual health by getting tested regularly, seeking treatment early, and talking with their partners and health providers about prevention options."
Because chlamydia often has no symptoms, regular testing is important, particularly for young adults who are at considerable risk.
First Nations Australians continue to be disproportionately affected by STIs. Compared with non-Indigenous Australians, they are diagnosed with chlamydia at more than 2.5 times the rate, gonorrhoea at more than four times the rate and syphilis at more than six times the rate.
"The gap in STI diagnoses between First Nations and non-Indigenous Australians remains deeply concerning, and in some areas, the disparity is widening," says Mr Robert Monaghan, Manager of the Yandamanjang First Nations Health Research Program at the Kirby Institute. "These are not simply statistics. They reflect ongoing inequities in access to culturally safe, trusted and appropriate sexual health services.
"We know what works. We need sustained investment in services that are accessible to First Nations communities and designed with communities, rather than for communities."
Modelling has shown that the introduction of First Nations-focused point-of-care testing programs can more than double the proportion of people treated and cured of an STI within two days. Since its 2013 launch, the point-of-care program is estimated to have led to reductions in both the risk of pelvic inflammatory disease and in preterm births among First Nations women in the communities where it is operating.
"Modelling suggests that point-of-care testing will reduce STI prevalence in remote Australian communities over the long term," says Mr Monaghan. "The First Nations Molecular Point-of-Care Testing Program has demonstrated how effective these interventions can be when local health services and communities are leading the response."
Chlamydia remains the most common sexually transmissible infection in Australia, with 94,184 cases in 2025. Unlike syphilis and gonorrhoea, diagnosis rates were similar among men and women, suggesting transmission is occurring across a broad range of sexual networks. Around half of chlamydia diagnoses were among people aged 20-29.
"Because chlamydia often has no symptoms, regular testing is important, particularly for young adults who are at considerable risk. Chlamydia is straightforward to diagnose, can be easily treated, and early treatment helps prevent complications and onward transmission," says Dr Skye McGregor.
"People who are sexually active can speak with a GP, sexual health clinic or Aboriginal Community Controlled Health Service about STI testing."
Concerning syphilis increases among women
While most syphilis diagnoses are among men (78% of diagnoses in 2025), syphilis is increasing at a much higher rate in women: a 167% increase among women compared to a 39% increase among men over the last decade.
"The rise in infectious syphilis in women is an urgent priority. While syphilis is entirely curable, untreated syphilis during pregnancy can lead to miscarriage, stillbirth or infants being born with congenital syphilis, which is when the infection is transmitted to an unborn child. Congenital syphilis is an extremely serious condition for infants that can result in significant lifelong health impacts, and in the most severe cases can be fatal," says Dr McGregor.
Curbing the disproportionate rates of congenital syphilis among First Nations people will require culturally safe, community-informed approaches that support women to access testing, treatment and antenatal care in ways that work for them in their communities.
There were 14 cases of congenital syphilis in 2025. There have been 113 cases of congenital syphilis over the past decade, with 40 resulting in the death of the infant.
Australia is aiming for zero congenital syphilis cases, and recent increases in the number of diagnoses have researchers, community groups, and health departments very concerned, leading to the declaration of syphilis as a communicable disease incident of national significance in 2025.
"With timely screening, syphilis can be cured and transmission prevented, so even one case of congenital syphilis is completely avoidable and unacceptable. National guidelines have recently been updated to recommend a minimum of three syphilis tests during pregnancy, and monitoring the impact of this change on congenital syphilis incidence will be critical," Dr McGregor says.
43% of all congenital syphilis cases in 2025 were diagnosed in First Nations infants (6 out of 14).
"Curbing the disproportionate rates of congenital syphilis among First Nations people will require culturally safe, community-informed approaches that support women to access testing, treatment and antenatal care in ways that work for them in their communities," says Mr Monaghan.
Jessica Michaels, the Deputy CEO of ASHM who provides support to the HIV, viral hepatitis and sexual health workforce, says every case of congenital syphilis is a tragedy and represents a failure of the healthcare system. "It's critical that national antenatal testing guidelines are consistently followed, to ensure congenital syphilis cases are identified early and treated before their potentially devastating consequences."
Gay and bisexual men remain a priority population
Men comprised 78% and 73% of cases of syphilis and gonorrhoea diagnoses respectively in Australia in 2025 - suggesting the majority of transmissions occur between men and demonstrating that gay and bisexual men are disproportionately affected by sexually transmitted infections.
Until recently, according to data received from a network of sexual health clinics (referred to as ACCESS), new infections of STIs in gay and bisexual men had been increasing. However, over the past three years, infectious syphilis diagnoses declined by 30% and 37% in HIV-negative and HIV-positive gay and bisexual men respectively. Similarly, chlamydia diagnoses declined by 31% and 26% among the two groups. Gonorrhoea diagnoses remained relatively stable over the last decade.
"The welcomed decline in syphilis and chlamydia among these groups likely reflects increasing use of doxycycline post-exposure prophylaxis - or doxy-PEP - an oral antibiotic that can be taken after a risk event to prevent those STIs. Its use and availability has increased since the release of the ASHM consensus statement in 2023," says Professor Andrew Grulich, head of the HIV Epidemiology and Prevention Program at the Kirby Institute.
"The longer-term trend of increases in STIs over the last two decades likely reflects a mix of factors, including more comprehensive screening and greater awareness and availability of highly effective HIV prevention strategies," says Prof. Grulich.
"However, the recent declines we are seeing are encouraging and suggest that prevention efforts are having an impact.
"We know how effective health promotion can be among gay and bisexual men as we have seen with the enormous reductions in HIV. We need to encourage increased targeted uptake of doxy-PEP to further drive down syphilis and chlamydia. People should continue with trusted methods for preventing gonorrhoea infection, such as condoms and regular testing, which they can access via sexual health clinics and community-based testing services."
