About chlamydia

Chlamydia is the most commonly diagnosed bacterial STI in Australia.Most notifications are among people aged 15-29.1

Chlamydia is often asymptomatic2 and research suggests that many chlamydia infections go undiagnosed.3

Untreated chlamydia can cause reproductive complications, particularly in women.

Approximately 15% of untreated infections will progress to symptomatic pelvic inflammatory disease (PID).4

PID can lead to chronic pelvic pain, ectopic pregnancy and tubal factor infertility.5-7

Repeat infections also increase the risk of progression to complications in women; each repeat infection increases a women’s risk of PID by 20%.8

Repeat infections are common. One quarter of women will be reinfected with chlamydia within four months of their initial infection9 and between 10-18% of men will be reinfected.10

The importance of partner management and retesting

Sexual partners from the previous six months should be notified of a chlamydia infection.11

There are many ways the index case can notify their partners – click here for more information. 

Partner notification can bring up tricky issues for patients, particularly if the infection has occurred within the context of an ostensibly monogamous relationship.

It is important to stress that a newly diagnosed infection is not necessarily a newly acquired one.12

More research on the natural history of chlamydia is needed, however, current research suggests that genital chlamydia infections can be present for months or years without causing symptoms.13,14

Australian guidelines recommend retesting for a chlamydia infection at 3 months.11

Less than a quarter of people aged 15-29 years are retested for a chlamydia reinfection after their initial diagnosis and treatment.3

Reinfection dramatically increases the risk of PID; retesting provides the opportunity to detect and treat reinfection early.8

Retesting is essential to catch reinfections early, and to prevent progression to complications, like PID.

Parter management and retesting are essential components of chlamydia control; they provide the opportunity to prevent ongoing transmission to the index cases sexual partner/s (and in turn, their sexual partner/s) and helps to prevents reinfection in the index case and progression to complications (like PID).

1. Australian Government Department of Health National Notifiable Diseases Surveillance System. Notification Rate of Chlamydial Infection, Australia, 2018 by age group and sex 2018 [Available from:]
2. Peipert JF. Genital Chlamydial Infections. N Engl. 2003;349(25):2424-30.
3. Gray RT, Callander D, Hocking JS, McGregor S, McManus H, Dyda A, et al. Population-level diagnosis and care cascade for chlamydia in Australia. Sex Transm Infect. 2019:sextrans-2018-053801.
4. Price M J, Ades A, Soldan K, et al. The natural history of Chlamydia trachomatis infection in women: a multi parameter evidence synthesis. Health Technol Assess. 2016;20(22).
5. Bateson D, Edmiston N. Pelvic Inflammatory Disease: Management of new-onset low abdominal pain in young women. Medicine Today. 2016;17(7):14-22.
6. Trojian TH, Lishnak TS, Heiman D. Epididymitis and Orchitis: An Overview. Am Fam Physician. 2009;79(7):583-7.
7. Gimenes F, Souza RP, Bento JC, et al. Male infertility: a public health issue caused by sexually transmitted pathogens. Nat Rev Urol. 2014;11:672.
8. Davies B, Ward H, Leung S, et al. Heterogeneity in Risk of Pelvic Inflammatory Diseases After Chlamydia Infection: A Population-Based Study in Manitoba, Canada. J Infect. 2014;210(Suppl 2):S549-S55.
9. Walker J, Tabrizi SN, Fairley CK, et al. Chlamydia trachomatis Incidence and Re-Infection among Young Women – Behavioural and Microbiological Characteristics. PLOS ONE. 2012;7(5):e37778.
10. Fung M, Scott KC, Kent CK, et alChlamydial and gonococcal reinfection among men: a systematic review of data to evaluate the need for retestingSexually Transmitted Infections 2007;83:304-309. Available from:
11. Australasian Sexual Health Alliance. Australian STI Management Guidelines for use in Primary Care 2018 [updated 29 March 2018; cited 2019 31st Jan]. Available from:
12. Fairley CK, Gurrin L, Walker J, Hocking JS. “Doctor, How Long Has My Chlamydia Been There?” Answer: “…. Years”. J Sex Transm Dis. 2007;34(9):727-8.
13. Australasian Society for HIV Viral Hepatitis and Sexual Health Medicine. Australasian Contact Tracing Guidelines 2016 [updated 2016; cited 2019 31st January]. Available from:
14. Fairley CK, Gurrin L, Walker J, Hocking JS. “Doctor, How Long Has My Chlamydia Been There?” Answer: “…. Years”. J Sex Transm Dis. 2007;34(9):727-8.

MoCCA is funded by the National Health and Medical Research Council (APP1150014) and is a collaboration between the University of Melbourne and our project investigators and partner organisations. Click here for a list of our collaborators.

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