Methods

Australia is a federation of 6 states (New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia) and 2 territories (the Australian Capital Territory and the Northern Territory).

State and territory health departments collect notifications of communicable diseases under their public health legislation. In September 2007, the National Health Security Act 2007¹ received royal assent. This Act provides a legislative basis for and authorises the exchange of health information, including personal information, between jurisdictions and the Commonwealth. The Act provides for the establishment of the National Notifiable Diseases List,² which specifies the diseases about which personal information can be provided. The National Health Security Agreement,³ signed by Health Ministers in April 2008, establishes operational arrangements to formalise and enhance existing surveillance and reporting systems, an important objective of the Act. Under the Agreement, in 2009 states and territories forwarded de-identified data on the nationally agreed set of 65 communicable diseases to the Department of Health and Ageing for the purposes of national communicable disease surveillance, although not all 65 diseases were notifiable in each jurisdiction. Data were renewed electronically from states and territories, daily or several times a week. The system was complemented by other surveillance systems, which provided enhanced information on various diseases, including four that are not reported to the National Notifiable Diseases Surveillance System (NNDSS).

In 2009, the NNDSS core dataset included the following 5 mandatory data fields: unique record reference number; notifying state or territory; disease code; confirmation status and the date when the public health unit was notified (notification receive date). In addition, the following core but non-mandatory data fields were supplied where possible: date of birth; age at onset; sex; Indigenous status; postcode of residence; disease onset date; date when the medical practitioner signed the notification form (notification date), death status, date of specimen collection and outbreak reference number (to identify cases linked to an outbreak). Where relevant, information on the species, serogroups/subtypes and phage types of organisms isolated, and on the vaccination status of the case were collected and reported to NNDSS. Data quality was monitored by the Office of Health Protection and the National Surveillance Committee (NSC) and there was a continual process of improving the national consistency of communicable disease surveillance through the daily, fortnightly and quarterly review of these data.

While not included in the core national dataset, enhanced surveillance information for some diseases (invasive pneumococcal disease, hepatitis C, tuberculosis and some sexually transmissible infections) were reported from states and territories to NNDSS but not included in this report. Additional information concerning mortality and specific health risk factors for some diseases were obtained from states and territories and included in this annual report.

Newly diagnosed HIV infection and AIDS were notifiable conditions in each state or territory health jurisdiction in 2009 and were forwarded to the National HIV Registry and National AIDS Registry at the Kirby Institute (formerly known as the National Centre in HIV Epidemiology and Clinical Research). Further information can be found in the Kirby Institute’s annual surveillance report.⁴

The surveillance for the classical and variant forms of Creutzfeldt-Jakob disease (CJD) in Australia is conducted through the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR) since its establishment in October 2003. CJD is a nationally notifiable disease and by June 2006, CJD was notifiable in all states and territories. Further surveillance information on CJD can be found in surveillance reports from the ANCJDR.⁵

Information from communicable disease surveillance is communicated through several avenues. The most up-to-date information on topics of interest is provided at fortnightly teleconferences of the Communicable Diseases Network Australia (CDNA) and a summary of these reports is available online from http://www.health.gov.au/cdnareport⁶ The Communicable Diseases Intelligence (CDI) quarterly journal publishes surveillance data and reports of research studies on the epidemiology and control of various communicable diseases.

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Notification rates for each notifiable disease were calculated using the estimated 2009 mid-year resident population supplied by the Australian Bureau of Statistics⁷ (ABS) (Appendix 1 and Appendix 2). Where diseases were not notifiable in a state or territory, national rates were adjusted by excluding the population of that jurisdiction from the denominator. For some diseases, age adjusted rates were calculated using either the direct method of standardisation for gastrointestinal diseases, or indirect method for sexually transmissible infections, with 2006 Census data as the standard population, (Map 1, Table 1).⁸ The Northern Territory was represented by Statistical Subdivisions (SSD) and in the case of Greater Darwin, by the combination of the Tiwi Islands, Darwin, Palmerston and Litchfield SSD. This combination helped preserve confidentiality while improving legibility at the printed map scale. The geocode 77777 for Greater Darwin is nominal.

Map 1: Australian Bureau of Statistics Statistical Division codes, Australia, and Statistical Subdivision codes, Northern Territory, 2009

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Table 1: Australian population by Statistical Division and Statistical Subdivision for the Northern Territory, 2009

SD code	Statistical Division	Population	SD code	Statistical Division	Population
Australian Capital Territory			South Australia
805	Canberra	351,868	405	Adelaide	1,187,466
New South Wales			410	Outer Adelaide	136,623
105	Sydney	4,504,469	415	Yorke and Lower North	47,052
110	Hunter	644,279	420	Murray Lands	70,426
115	Illawarra	431,160	425	South East	65,978
120	Richmond–Tweed	241,954	430	Eyre	35,556
125	Mid-North Coast	309,588	435	Northern	80,489
130	Northern	184,822	Tasmania
135	North Western	118,535	605	Greater Hobart	212,019
140	Central West	183,157	610	Southern	37,456
145	South Eastern	216,593	615	Northern	141,434
150	Murrumbidgee	158,593	620	Mersey–Lyell	112,383
155	Murray	118,540	Victoria
160	Far West	22,731	205	Melbourne	3,995,537
Northern Territory (Subdivisions)			210	Barwon	285,096
71005	Finniss	2,865	215	Western District	106,268
71015	Alligator	6,806	220	Central Highlands	155,585
71025	East Arnhem	16,070	225	Wimmera	50,878
71030	Lower Top End NT	23,868	230	Mallee	94,736
71040	Central NT	40,967	235	Loddon	183,659
77777	Greater Darwin	127,285	240	Goulburn	210,114
Queensland			245	Ovens–Murray	99,872
305	Brisbane	2,004,262	250	East Gippsland	86,812
307	Gold Coast	515,157	255	Gippsland	174,671
309	Sunshine Coast	323,423	Western Australia
312	West Moreton	94,660	505	Perth	1,658,992
315	Wide Bay–Burnett	287,425	510	South West	246,202
320	Darling Downs	237,211	515	Lower Great Southern	58,851
325	South West	26,277	520	Upper Great Southern	19,169
330	Fitzroy	220,714	525	Midlands	55,730
335	Central West	12,270	530	South Eastern	58,727
340	Mackay	172,735	535	Central	64,849
345	Northern	227,340	540	Pilbara	47,528
350	Far North	269,650	545	Kimberley	35,009
355	North West	33,979	Other territories		–
			Australia	Total	21,944,741

Source: Australian Bureau of Statistics. Population by Age and Sex, Regions of Australia, 2009; 2010. ABS Catalogue: 3235.0.⁸

Notifications were summed by the postcode weighting calculated by the ABS Postcode Concordance.⁹ These ABS concordance data were used to proportionally allocate notifications into SDs/SSDs according to the percentage of the population of the postcode living in the region. The total notifications per region are displayed in the relevant area.

Disease rates were calculated per 100,000 population for the relevant areas using ABS population data.⁷ Rates were mapped for different SDs and ordered into five groups using the Jenks Natural Breaks method whereby the largest breaks between natural clusters of ordered data were identified and used as class boundaries. A class ‘0’ was added to account for areas with no notifications, for a total of six rate classes per map. Note that the classification is data dependent and changes from map to map.