Sexually transmissible infections
Why are sexually transmissible infection rates important?
Sexually transmissible infections (STIs) remain a major public health concern, contributing to significant long-term morbidity (Bowden et al. 2002; DoH 2014). A number of factors put adolescents at higher risk of STIs, including a lack of knowledge about them, inconsistent condom use, lack of communication and negotiation skills which can make condom use difficult. Biologically, young people may be more vulnerable to STIs due to immature reproductive and immune systems (Sales & DiClemente 2010).
Australia has made progress in the management of STIs with successful education campaigns and safe and effective treatments available for many types. However, some STIs are increasing, indicating that messages about safer sexual practices are not always meeting their mark. The Third National Sexually Transmissible Infections Strategy 2014–2017 aims to reduce sexually transmissible infections (STI) and blood borne viruses (BBV), and the morbidity, mortality and personal and social impacts they cause.
The STIs reported to the NNDSS and included in this portal are chlamydia, gonorrhoea and syphilis. Donovanosis is now rare in Australia (NNDSS 2012) and is not included.
Do rates vary across population groups?
Chlamydia is the most commonly notified STI among young people in Australia. In 2013, the notification rate was 1,275 per 100,000 for all young people. The rate was 4 times as high among 18–24 year olds as 12–17 year olds (1,889 compared to 468 per 100,000). Notifications for females were twice as high as males (1,726 compared to 846 per 100,000).
The notification rate for gonorrhoea all young people in 2013 was 149 per 100,000. The rate for 18–24 year olds was almost 3 times as high as that for 12–17 year olds (207 compared to 72 per 100,000). Males had a higher notification rate than females (168 compared to 129 per 100,000). Of the different population groups, the greatest disparity in gonorrhoea notification rates was between Indigenous and Other Australian young people (1,359 per 100,000 compared to 88 per 100,000 respectively).
In 2013, there were 12 notifications for syphilis per 100,000 young people. The rate for 18–24 year olds was almost 6 times as high as that for 12–17 year olds (19 per 100,000 compared to 3 per 100,000). The rate for males was 3 times as high as the rate for females (18 per 100,000 compared to 6 per 100,000). Indigenous youths had notably higher rates of syphilis infection compared to Other Australian youths (62 per 100,000 compared to 9.5 per 100,000).
Has there been a change over time?
Between 2005 and 2013 the notification rate for chlamydia among all young people peaked at 1,338 per 100,000 in 2011 and declined to 1,275 per 100,000 in 2013. These trends are largely consistent across all population groups.
Notification rates for gonorrhoea increased from 94 per 100,000 in 2008 and to a peak of 150 per 100,000 in 2012 where the rate has plateaued. For different age groups and sexes, there appears to be an increase in the notification rates in 18–24 year olds and young males since 2012, whereas there has been a decrease in the notification rates for 12–17 year olds and females over this period. From 2005 to 2013, there has been a steady increase in gonorrhoea notification rates among Other Australian young people (from 36 in 2005 to 88 per 100,000 in 2013). Trends for Indigenous young people are less evident due to large fluctuations between years, although the rate appears to have decreased from 1,648 per 100,000 in 2011 to 1,359 per 100,000 in 2013.
The notification rate for syphilis increased in recent years from 7 per 100,000 in 2010 to 12 per 100,000 in 2013. This trend is also apparent in 18–24 year olds over this period, whereas the notification rate for has relatively steady for 12–17 year olds since 2011. The notification rate for males increased from 10 per 100,000 in 2010 to 18 per 100,000 in 2013, while the rate among young females has declined from 7 per 100,000 in 2011 to 6 per 100,000 in 2013.
Between 2005 and 2013 there has been a steady increase in the syphilis notification rate for Other Australian young people from 4 to 10 per 100,000. Over the same period, the notification rate for Indigenous young people has fluctuated, with values ranging from 140 to 42 per 100,000. In recent years the syphilis notification rate for Indigenous young people has declined from 78 per 100,000 in 2011 to 62 per 100,000 in 2013.
Syphilis notification rates include both infectious syphilis (primary, secondary or early latent) of less than 2 years duration and syphilis of more than 2 years or unknown duration. Syphilis notification rates exclude congenital syphilis.
In interpreting these data it is important to note that changes in notifications over time may not solely reflect changes in disease prevalence or incidence. Changes in testing policies; screening programs, including the preferential testing of high risk populations; the use of less invasive and more sensitive diagnostic tests; and periodic awareness campaigns, may influence the number of notifications that occur over time.
Determination of Indigenous status is by descent, self-identification and community. The ‘Other Australians’ population group includes both non-Indigenous youths and youths whose Indigenous status was unknown. For further information on the determination of Indigenous status, see Source data tables: NYIF indicators.
Indigenous status data were only presented in instances where the completeness of the data was greater than 50%. For more information see Source data tables: NYIF indicators.
Due to the high proportion of asymptomatic presentations of STI infections, diagnoses are heavily influenced by testing patterns. High rates of STI diagnoses in Indigenous populations may be due to higher levels of screening and not necessarily associated with increased levels of transmission among Indigenous persons.
Additionally, the differences in rates between females and males should be interpreted with caution, as rates for testing for STI infections, symptom status, health care-seeking behaviours, and partner notification differ between the sexes.
National Notifiable Diseases Surveillance System, unpublished data
Bowden FJ, Tabrizi SN, Garland SM & Fairley CK 2002. Infectious diseases. 6: sexually transmitted infections: new diagnostic approaches and treatments. Medical Journal of Australia 176(11):551–7.
Department of Health (DoH) 2014. Third National Sexually Transmissible Infections Strategy 2014–2017. Canberra: Commonwealth of Australia.
Sales JM & DiClemente RJ 2010. Research facts and findings. New York: ACT for Youth Center of Excellence.