In the past decade, syphilis and gonorrhoea cases in Australia more than doubled, chlamydia diagnoses remain high and HIV diagnoses declined, according to the latest data released by the Kirby Institute at UNSW Sydney.
The latest national surveillance data on sexually transmitted infections (STIs) was released today at the Australasian HIV&AIDS Conference in Adelaide.
"Sexually transmissible infections can be passed on to others, but in most instances can be easily treated," says the report's lead author Dr Skye McGregor, an epidemiologist based at the Kirby Institute and UNSW.
"However, if left untreated sexually transmissible infections can cause serious long-term health concerns like pelvic inflammatory disease and infertility in women," Dr McGregor says.
"Importantly, people who are pregnant can pass on the infection to their babies causing serious harm."
She presented the data at the conference today, with the numbers not only highlighting areas of public health concern but where to focus efforts.
A recent analysis from the Australian Survey of Health and Relationships (ASHR) found only 16% of Australians aged 16-49 years had ever been tested for an STI, with only one in two having ever discussed sexual health with their health care providers.
"These data, on a backdrop of rising STIs, are concerning," Dr McGregor says. "Chlamydia, gonorrhoea and syphilis are easily treated and cured with antibiotics. HIV, while not curable, is highly treatable.
"Diagnosis and starting effective treatment early prevents poor health outcomes and interrupts onward transmission."
She says regular sexual health testing helps reduce the risk of serious outcomes - as well as implementing safety measures for all, such as using condoms.
"For gay and bisexual men, doxy PEP is also available, which involves taking the antibiotic, doxycycline, within 72 hours of sex to reduce the risk of bacterial sexually transmitted infections - particularly syphilis and chlamydia.
"It's important that everyone who is sexually active discusses sexual health with their partners, practises safe sex, has regular STI testing - and talks to their health care provider about their sexual health."
Syphilis and congenital syphilis increasing
There were 5866 diagnoses of syphilis in 2024 in Australia - double the number of diagnoses in 10 years. While 80% of diagnoses were among men, syphilis diagnoses among women quadrupled in the past decade.
The researchers say the increases among women of childbearing age are particularly concerning.
"If untreated in pregnancy, infection can lead to miscarriage or stillbirth, or congenital syphilis, which is when the infection is transmitted to an unborn child," Dr McGregor says.
"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."
Congenital syphilis cases have more than doubled since 2015, with 34 attributable infant deaths in that time. Of the deaths, more than half were among First Nations Australians.
Last month, Australia's Chief Medical Officer and Director of the International Centre for Future Health Systems (ICFHS) at UNSW Sydney, Professor Michael Kidd, declared syphilis a Communicable Disease Incident of National Significance - particularly due to concerns about congenital syphilis.
"By raising awareness among Australians - including healthcare professionals - we will help ensure more people get tested and treated for syphilis, so we can stop the spread of the disease," Prof. Kidd says.
Jessica Michaels - Australasia Society for HIV, Viral Hepatitis, and Sexual Health Medicine (ASHM) Deputy CEO - says the syphilis epidemic will need a sustained and coordinated response to resolve, "from government, researchers, the clinical workforce and the community."
It's important that everyone who is sexually active discusses sexual health with their partners, practises safe sex, has regular STI testing - and talks to their healthcare provider about their sexual health.
Gonorrhea also on the rise
There were 44,210 gonorrhoea diagnoses in Australia in 2024 - also a doubling of cases in the past 10 years. 70% of diagnoses were in men, at a rate higher among males than females for every year in the past decade.
"The disproportionately high number of gonorrhoea diagnoses among men compared to women indicates more frequent transmission through male-to-male sex," says Professor Andrew Grulich, head of the HIV Epidemiology and Prevention Program at the Kirby Institute.
"It is likely that the increases can be explained by the availability of highly effective HIV prevention strategies, and a subsequent gradual decline in the use of condoms, together with more comprehensive STI screening."
Chlamydia - Australia's most common STI - stable
In 2024, there were 101,742 diagnoses of chlamydia in Australia. Around half were among people aged 20-29 years.
"Although chlamydia diagnoses are not increasing at the same pace as syphilis or gonorrhoea, it is still the most common STI in Australia," says Dr McGregor. "If you are sexually active, particularly with a new partner, STI testing is crucial. A test for chlamydia is very straightforward and the treatment is usually a single dose of antibiotics."
Higher rates among Australia's First Nations peoples
Rates of sexually transmissible infections remain high among First Nations Australians, with chlamydia diagnosed at more than twice the rate, gonorrhoea almost four times higher, and syphilis more than five times higher than in non-Indigenous people.
"These gaps are even starker in regional and remote areas," says Robert Monaghan , a Bundjalung-Gumaynggir man and Manager of the Yandamanjang First Nations Health Research Program at the Kirby Institute.
"What's needed now is real investment in culturally safe, community-driven health promotion, testing and treatment," he says.
"Declaring syphilis a Communicable Disease Incident of National Significance is an important step. Sustainable change depends on culturally safe, community-led action."
HIV diagnoses down - but still more to do
There were 757 HIV diagnoses in 2024, a 27% decline in the past decade. 62% of diagnoses were attributable to sex between men, 27% to sex among heterosexuals and 3% to injecting drug use.
While 10-year trends show an overall decline, there was a small increase in diagnoses in the past two years.
"While the small increase is likely related to unusually low diagnoses during the COVID pandemic, during which there was a marked decline in both transmission risks and testing, the small increase is a reminder that Australia's HIV transmission elimination journey is not over. We must enhance our elimination efforts," says Dr McGregor.
Scott Harlum, President of the National Association of People with HIV Australia , says while numbers of new HIV diagnoses are consistent with a decline over the past decade, there's still much more to do to achieve the virtual elimination of domestic HIV transmissions in Australia by 2030.
"It's also important to remember that each of the 757 diagnoses are individuals," he says. "There is a face and a name behind every one of those 'data' - each with lived experience of the reasons why health systems have failed to prevent HIV transmission.
"This reinforces the critical importance of people with HIV sharing our lived experience so that we can build a better understanding of HIV and effectively plan a response which enables year-on-year declines in new cases until we reach the virtual elimination goal."
Dash Heath-Paynter, CEO of Health Equity Matters , says achieving this goal needs a renewed focus - while community leadership has helped drive down the rate of HIV infections, some are still left behind.
"HIV diagnoses have almost halved among Australian-born people over the past decade. However, for people born outside Australia, no reduction in HIV diagnoses was observed over the same period," he says.
"We need to urgently implement health services that are co-designed by the very people they serve. This is the best way to raise awareness of HIV among overseas-born people, increase the use of proven HIV prevention strategies and testing, and improve access to care."
In 2024, almost one-third of HIV diagnoses were considered late. This means the person diagnosed may have lived with HIV for at least four years without knowing their status while experiencing HIV-related illnesses. Among heterosexuals, 51% of HIV diagnoses were classified as late.
"We need to ensure HIV testing is accessible, including self-testing, to ensure timely diagnosis and engagement in appropriate care for people with HIV," says Dr McGregor.
Although HIV diagnoses among First Nations peoples declined by 43% in the past decade, the report's authors suggest these trends should be interpreted with caution as the numbers are low year-on-year.
