Tuesday, 29 November 2016

Geography and socioeconomic status put Australians at risk of infectious diseases

Dr Katherine Gibney, who recently completed her PhD at SPHPM, attracted media interest with a paper she wrote on sociodemographic inequities in infectious disease notifications. 

The paper, “Sociodemographic and geographical inequalities in notifiable infectious diseases in Australia: a retrospective analysis of 21 years of national disease surveillance data” was published in the Lancet Infectious Diseases journal and was co-authored with SPHPM researchers Professor Allen Cheng, Dr Robert Hall and Professor Karin Leder.

The unique world-first study examined 21 years of data and more than 2.4 million cases of infectious disease across Australia, revealing the adverse role being poorer, living remotely or being an Indigenous Australian plays in rates of sexually transmissible infections (STIs), diseases that can be vaccinated against or Hepatitis B and C. Data was taken from the National Notifiable Disease Surveillance System (NNDSS), a surveillance system that Dr Hall was involved in establishing in 1991.

Dr Gibney said that remote living and one’s socioeconomic status were both associated with higher notification incidence for infectious diseases, with people living in remote areas of Australia three times more likely to have a notifiable disease with the incidence of STIs six times higher in these regions.

“STIs were the most over-represented disease group among remote-living Australians. Notification incidence of gonococcal infection was 20 times higher in remote areas compared to cities or regional areas. Gastrointestinal infections were also more common in remote areas, with salmonellosis incidence 3.5 times higher in remote than non-remote areas,” said Dr Gibney.

STIs comprised 33 per cent of all notifications, increasing fivefold from 64/100 000 per year in 1991-1997 to 334/100 000 per year in 2005-2011. Chlamydia accounted for 79 per cent of STI notifications, gonococcal infection 16 per cent and syphilis 5 per cent.

The study painted a stark picture of the over representation of Indigenous Australians: while only making up only 3 per cent of the population, Indigenous Australians represent 8 per cent of notified cases. The researchers pointed out that this is probably an underestimation due to the under-reporting that takes place for Indigenous Australians, sometimes through lack of access to services.

“We need to ensure that Indigenous status is recorded for all notified cases across the country to enable meaningful national analysis of this important issue. Not being able to measure the size of the problem hinders our ability to fix the problem,” said Dr Gibney.

The annual number of notifications increased more than fivefold over the 21-year study period. Researchers said the reasons for this increase can be attributed to various factors including the addition of notifiable diseases to notification lists, population growth, introduction of screening programs and improved diagnostics, as well as true changes in disease incidence.

Researchers were happy to point out that the data also highlights significant public health achievements, particularly the success of the National Immunisation Program, as demonstrated by the marked reduction in notification incidence for rubella, measles and Hib (which causes meningitis).

“This study gives a really good overview of the status of notifiable infectious diseases in Australia and provides some clear evidence that more needs to be done to eliminate disparities in the burden of infectious diseases in Australia.

“In particular, attention needs to focus on remote living and Indigenous Australians for many disease groups but in particular STIs and gastrointestinal diseases, while socioeconomically disadvantaged areas should be the focus of efforts to diagnose, treat, and prevent transmission of hepatitis B and C,” said Dr Gibney.

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