Australia's notifiable diseases status, 2009: Annual report of the National Notifiable Diseases Surveillance System - Methods

The Australia’s notifiable diseases status, 2009 report provides data and an analysis of communicable disease incidence in Australia during 2009. The full report is available in 16 HTML documents. The full report is also available in PDF format from the Table of contents page.

Page last updated: 22 August 2011

This article was published in Communicable Diseases Intelligence Vol 35 Number 2, June 2011 and may be downloaded as a full version PDF file (1854 KB).

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

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.

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