Australia's notifiable diseases status, 2010: Annual report of the National Notifiable Diseases Surveillance System - Methods

The Australia’s notifiable diseases status, 2010 report provides data and an analysis of communicable disease incidence in Australia during 2010. 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: 25 June 2012

This extract of the NNDSS annual report 2010 was published in Communicable Diseases Intelligence Vol 36 No 1 March 2012. A print friendly full version may be downloaded as a PDF 1862 KB.

The full issue of CDI is available as a PDF file (2586 KB) or by individual articles from this issue's table of contents

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 respective 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 which was drafted in 2007 and 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 2010 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.

In 2010, the National Notifiable Diseases Surveillance System (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 central agency in the jurisdiction 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 B, 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 2010 and were forwarded to the Kirby Institute for infection and immunity in society. 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.

Notification rates for each notifiable disease were calculated using the estimated 2010 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 the direct method of standardisation. for gastrointestinal diseases, or indirect method for sexually transmissible infections, with 2006 census data as the standard population. All rates are represented as the rate per 100,000 population unless stated otherwise.

The 2 maps produced for this report (chlamydia and pertussis) were created with ArcGIS mapping software (ESRI, Redlands, CA) and based on the NNDSS notifications’ residential postcode. Notifications were summed by the postcode weighting calculated by the ABS Postcode Concordance.8 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.

With one exception, all jurisdictions in the Australian map consist of Statistical Divisions (SD) as defined by the Australian Standard Geographical Classification (Map 1, Table 1). 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 SSDs. This combination helps preserve confidentiality while improving legibility at the scale of the maps to be printed. The geocode 77777 for Greater Darwin is only nominal.

Map 1: Australian Bureau of Statistics Statistical Division codes, Australia, and Statistical Subdivision codes, Northern Territory, 2010

Australian Bureau of Statistics Statistical Division codes, Australia, and Statistical Subdivision codes, Northern Territory, 2010

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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
1,203,186
810 ACT balance
Included above
410 Outer Adelaide
139,489
New South Wales
415 Yorke and Lower North
47,585
105 Sydney
4,575,532
420 Murray Lands
70,705
110 Hunter
651,622
425 South East
66,724
115 Illawarra
436,117
430 Eyre
35,892
120 Richmond–Tweed
244,085
435 Northern
81,001
125 Mid-North Coast
313,322
Tasmania
130 Northern
186,496
605 Greater Hobart
214,705
135 North Western
119,329
610 Southern
37,838
140 Central West
184,921
615 Northern
142,311
145 South Eastern
219,655
620 Mersey–Lyell
112,789
150 Murrumbidgee
159,624
Victoria
155 Murray
119,302
205 Melbourne
4,077,036
160 Far West
22,584
210 Barwon
290,277
Northern Territory (Subdivisions)
215 Western District
107,072
71005 Finniss
2,906
220 Central Highlands
158,627
71015 Alligator
6,908
225 Wimmera
50,903
71025 East Arnhem
16,252
230 Mallee
95,213
71030 Lower Top End NT
24,170
235 Loddon
186,201
71035 Barkly
8,137
240 Goulburn
212,799
71040 Central NT
41,272
245 Ovens–Murray
101,086
77777 Greater Darwin
130,066
250 East Gippsland
87,872
Queensland
255 Gippsland
178,846
305 Brisbane
2,043,185
Western Australia
307 Gold Coast
527,828
505 Perth
1,696,065
309 Sunshine Coast
330,934
510 South West
253,512
312 West Moreton
97,414
515 Lower Great Southern
59,412
315 Wide Bay–Burnett
293,455
520 Upper Great Southern
19,100
320 Darling Downs
241,537
525 Midlands
56,435
325 South West
26,489
530 South Eastern
59,070
330 Fitzroy
223,516
535 Central
65,600
335 Central West
12,387
540 Pilbara
48,610
340 Mackay
176,236
545 Kimberley
35,706
345 Northern
231,628
Other territories
350 Far North
275,058
Australia Total
22,326,388
355 North West
34,183
     

Source: ABS 3235.0 Regional Population Growth, Australia, 4 August 2011.8

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 5 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 6 rate classes per map. Note that the classification is data dependent and changes from map to map.

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