Why chlamydia in Australia is on the rise

Chlamydia is the most commonly reported sexually transmitted infection in Australia, and the numbers are heading in the wrong direction. Over the past decade chlamydia rates have risen by around 17.8%, and in 2024 alone there were more than 101,000 diagnosed cases, with roughly half occurring in people aged 20 to 29. So why are cases climbing, and what will it take to turn the trend around?

What is chlamydia?

Chlamydia is a bacterial infection usually passed on through vaginal, oral and anal sex, and also through sharing sex toys or genital-to-genital contact. Babies born to mothers with chlamydia can contract it during birth. It can affect the cervix, urethra, testicles, throat, anus and eyes.

Most people with chlamydia have no symptoms at all, which is a big part of why it spreads so easily. Left untreated it can cause serious complications, including pelvic inflammatory disease (PID) and infertility in women. The good news is that chlamydia is easily cured with antibiotics once it’s found. If you want the full picture of what untreated infection can lead to, see our guide to the long-term risks of chlamydia.

How common is chlamydia in Australia?

Anyone who is sexually active can get chlamydia, but it’s most common in young people. In 2024, around half of all diagnoses were in people aged 20 to 29, and women aged 15 to 29 are the group most affected of all.

What other groups are affected by chlamydia?

Like other STIs, chlamydia isn’t spread evenly across the country. Cities report higher raw numbers, but rates in regional and remote areas are disproportionately high for their population, driven by factors such as reduced access to healthcare and less sexual health education.

The burden also falls more heavily on Aboriginal and Torres Strait Islander peoples, who experience higher rates of STIs overall, with chlamydia rates around twice those of non-Indigenous Australians.

Why is chlamydia in Australia increasing?

Several factors are contributing to the rise.

Declining condom use

As HIV pre-exposure prophylaxis (PrEP) has become widely available, fewer people are using condoms. Older Australians starting new relationships are also less likely to use them once pregnancy is no longer a concern. Condoms and dental dams remain one of the most effective ways to prevent chlamydia and other STIs with new or casual partners.

Lower awareness of STIs and testing

The COVID-19 pandemic disrupted sexual health education and reduced testing, as access to services narrowed. Gaps in knowledge and missed tests mean people can acquire and pass on chlamydia without realising.

Stigma

There is still stigma attached to an STI diagnosis, and it can stop people seeking advice and treatment even when they notice symptoms. Care that is confidential and judgement-free helps break that barrier down.

Asymptomatic infection

Because chlamydia so often causes no symptoms, many people simply don’t know they have it, and unknowingly pass it to partners. This is the single biggest driver of ongoing transmission.

How can we prevent chlamydia?

Bringing the numbers down takes a mix of public-health strategies, and the most important is regular STI testing alongside safer sex, including condom use. Ongoing campaigns to reduce the stigma of testing make it easier and less embarrassing to seek care.

Regular testing and re-testing

While most of us can’t influence public-health policy, we can all play our part through safer sex and regular STI testing, both proven ways to reduce transmission in the community.

Re-testing matters too. In 2023, 91% of people diagnosed with chlamydia were tested, but only 26% were re-tested afterwards. Because re-infection is common, re-testing around three months after treatment is recommended. If a partner has been diagnosed, partner treatment (PDPT) can help stop the cycle of re-infection.

Not sure when you should be tested?

Regular testing is the single most effective thing you can do. As a guide:

• At least yearlyAnyone who’s sexually active, even with a single partner.
• Every 3 monthsIf you have multiple partners, or you’re a man who has sex with men (even if you use condoms).
• After treatmentRe-test about 3 months after treatment, because re-infection is common.

If a partner has tested positive, partner treatment (PDPT) can help stop the cycle of re-infection.