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25 Oct 2016

Research reveals poor infectious disease scorecard with remote and poor Australians at greater risk

A unique 20+ year study of more than 2.4 million cases of infectious disease across Australia reveals a major social divide where being poorer, living remotely or being an Indigenous Australian means having an increased risk of sexually transmissible infections (STIs), diseases that can be vaccinated against or hepatitis B and C.

The study by Dr Katherine Gibney from the Peter Doherty Institute for Infection and Immunity (a joint venture between The University of Melbourne and The Royal Melbourne Hospital) and Dr Robert Hall, Professor Allen Cheng and Professor Karin Leder from the Monash Department of Epidemiology and Preventive Medicine found that people living in remote areas of Australia are three times more likely to have a notifiable disease with the incidence of STIs six times higher in these regions according to the study, published today in The Lancet Infectious Diseases (embargo 9.30 am Tuesday 25/10 AEST).

Earlier analysis of these data showed people living in Queensland and the Northern Territory (NT) were disproportionally represented on the infectious diseases scorecard. Queensland had the greatest number of notifications despite ranking third in population behind New South Wales (NSW) and Victoria. The NT had notification rates four times higher than the national average and the annual incidence of STIs was eightfold higher in the NT than the national average according to previous studies conducted by the researchers.

The authors warn that the incidence of communicable disease nationally after two decades of surveillance and state and territory based health programs remains “unacceptably high” in remote and lower socio economic areas.

The study - a world first in providing the longest and most comprehensive trend analysis of all nationally notifiable diseases including influenza, gastrointestinal diseases and STIs – used data from the National Notifiable Disease Surveillance System (NNDSS), a surveillance system that Dr Hall was instrumental in setting up in 1991.

In Australia, notification of selected infectious diseases is required by public health legislation in the six states and two territories. Each jurisdiction defines its own notification list and receives data from doctors and/or laboratories. Jurisdictions forward de-identified notification data for cases meeting national case definitions for diseases on the National Notifiable Diseases List (NNDL) to the NNDSS.

The researchers reviewed the first 21 years (1991–2011) of the NNDSS, collecting data on all nationally notified diseases except HIV and AIDS and Creutzfeldt–Jakob disease. More than 2.4 million cases were analysed by disease group, jurisdiction (six states and two territories), Indigenous status, age group and notification year.

The bulk of the NDSS was made up of eight diseases, each recording more than 100,000 cases over the twenty plus years in the study. These diseases included chlamydia, campylobacteriosis (a form of gastroenteritis), hepatitis B and C, influenza, pertussis (whooping cough), salmonellosis, and gonococcal infection.  

The annual number of notifications increased more than fivefold over the 21-year study period. According to Dr Gibney, the reasons for this increase “are multifactorial, including the addition of notifiable diseases to national and jurisdictional notification lists, population growth, introduction of screening programs (such as for chlamydial infection), and improved diagnostics, as well as true changes in disease incidence.”

STIs comprised 33% 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% of STI notifications, gonococcal infection 16% and syphilis 5%.

The study reveals that while Indigenous people make up only 3% of the Australian population they represent 8% of notified cases.

“Significant under-reporting of Indigenous status among notified cases means likely underestimation of this proportion despite completeness of Indigenous status reporting in health data sets being a priority in the Federal Government’s Closing the Gap strategy,” according to Dr Gibney.

According to the architect of the Surveillance Database, Dr Hall, the study results also revealed the success of the national immunisation strategy.

“The study highlights some major public health achievements. The marked reduction in notification incidence for rubella, measles and Hib (which causes meningitis) demonstrate the impact of Australia’s National Immunisation Program,” he said.

CLICK HERE to listen to a podcast on The Lancet Infectious Diseases website outlining this research.