Epidemiology: What regions and populations have been affected

Epidemiology  is the study of which groups and where these groups of people experience a particular health related event.  Different approaches are used to work this out including surveys and notification data for diseases like syphilis.  This information is necessary to inform public health responses, determine public health priorities and develop evidence-based policy, which is essential information for:

• outbreak management
• identifying public health priorities
• developing focused evidence based policy

Throughout 2013-2017, the notification rate of infectious syphilis in the Australian population has increased by 135%.  This increase is largely attributed to outbreaks occurring in two different populations:

• Young (15-34 year old) heterosexual Aboriginal and Torres Strait Islander people residing in predominately regional and remote areas in Northern and Central Australia.
• Non-Indigenous men who have sex with men (MSM) residing primarily in urban areas.

An increase in notification of infectious syphilis in Aboriginal and/or Torres Strait Islander Peoples has been seen across all age brackets.  The increases between 2015 and 2019, were as follows:

• aged 15 to 19 has increased by 90%
• aged 20-24 has increased by 45.7%
• aged 25-29 has increased by 101%
• aged 30-39 has increased by 145%
• over 40 years old increased by 219%

Among Aboriginal and Torres Strait Islander women of reproductive age (15-44 years), the inefctious syphilis notification rate steadily increased from 94.6 per 100 000 women in 2015 to 227.8 per 100 000 women in 2019, an increase of over 140%.

In 2017, the notification rate in the Aboriginal and Torres Strait Islander population was almost 7 times higher than the non-Indigenous population.  In remote and very remote areas, this increases to 27 times higher.  The greatest proportion of syphilis notifications nationally are in non-Indigenous males (approximately 70% in 2017), however, the distribution of cases within the Aboriginal and Torres Strait Islander population is disproportionately higher (number of cases per 1000 000 population).

Infectious Syphilis Notifications

Rate Per 100 000, 2009-2018, Aboriginal and Torres Strait Islander Status