This article {extract} was published in Communicable Diseases Intelligence Vol 30 No 1 March 2006 and may be downloaded as a full version PDF from the Table of contents page.

Introduction

Australia's notifiable diseases status, 2004, is an annual surveillance report of nationally notifiable communicable diseases. Communicable disease surveillance in Australia operates at the national, state and local levels. Primary responsibility for public health action lies with the state and territory health departments. The role of communicable disease surveillance at a national level includes:

•  identifying national trends;

•  guidance for policy development and resource allocation at a national level;

•  monitoring the need for and impact of national disease control programs;

•  coordination of response to national or multi-jurisdictional outbreaks;

•  description of the epidemiology of rare diseases, that occur infrequently at state and territory levels;

•  meeting various international reporting requirements, such as providing disease statistics to the World Health Organization (WHO), and;

•  support for quarantine activities, which are the responsibility of the national government.

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Methods

Australia is a federation of six states ( New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia) and two territories (the Australian Capital Territory and the Northern Territory). State and Territory health departments collect notifications of communicable diseases under their public health legislation. The Australian Government Department of Health and Ageing ( DoHA) does not have any legislated responsibility for public health apart from human quarantine. States and territories voluntarily forward data on a nationally agreed set of communicable diseases to DoHA for the purposes of national communicable disease surveillance.

Sixty communicable diseases (Table 1) agreed upon nationally through the Communicable Diseases Network Australia (CDNA) are reported to the National Notifiable Diseases Surveillance System (NNDSS). The system is complemented by other surveillance systems, which provide information on various diseases, including some that are not reported to NNDSS.

Table 1. Diseases notified to the National Notifiable Diseases Surveillance System, Australia, 2004

Disease	Data received from
Bloodborne diseases
Hepatitis B (incident)	All jurisdictions
Hepatitis B (unspecified)*	All jurisdictions except NT
Hepatitis C (incident)	All jurisdictions except Qld and NT
Hepatitis C (unspecified)*,†	All jurisdictions
Hepatitis D	All jurisdictions
Gastrointestinal diseases
Botulism	All jurisdictions
Campylobacteriosis‡	All jurisdictions except NSW
Cryptosporidiosis	All jurisdictions
Haemolytic uraemic syndrome	All jurisdictions
Hepatitis A	All jurisdictions
Hepatitis E	All jurisdictions
Listeriosis	All jurisdictions
Salmonellosis (NEC)	All jurisdictions
Shigellosis	All jurisdictions
SLTEC, VTEC§	All jurisdictions
Typhoid	All jurisdictions
Quarantinable diseases
Cholera	All jurisdictions
Plague	All jurisdictions
Rabies	All jurisdictions
Severe acute respiratory syndrome	All jurisdictions
Smallpox	All jurisdictions
Tularaemia	All jurisdictions except ACT
Viral haemorrhagic fever	All jurisdictions
Yellow fever	All jurisdictions
Sexually transmissible infections
Chlamydial infections (NEC)||	All jurisdictions
Donovanosis	All jurisdictions
Gonococcal infection	All jurisdictions
Syphilis (all categories)	All jurisdictions
Syphilis < 2 years duration	All jurisdictions
Syphilis > 2 years or unknown duration	All jurisdictions
Syphilis – congenital	All jurisdictions
Vaccine preventable diseases
Diphtheria	All jurisdictions
Haemophilus influenzae type b	All jurisdictions
Influenza (laboratory confirmed)¶	All jurisdictions
Measles	All jurisdictions
Mumps	All jurisdictions
Pertussis	All jurisdictions
Pneumococcal disease (invasive)	All jurisdictions
Poliomyelitis	All jurisdictions
Rubella	All jurisdictions
Rubella – congenital	All jurisdictions
Tetanus	All jurisdictions
Vectorborne diseases
Barmah Forest virus infection	All jurisdictions
Dengue	All jurisdictions
Flavivirus (NEC)**	All jurisdictions except ACT
Japanese encephalitis virus	All jurisdictions
Kunjin virus††	All jurisdictions except ACT
Malaria	All jurisdictions
Murray Valley encephalitis virus	All jurisdictions except ACT
Ross River virus infection	All jurisdictions
Zoonoses
Anthrax	All jurisdictions
Australian bat lyssavirus	All jurisdictions
Brucellosis	All jurisdictions
Leptospirosis	All jurisdictions
Lyssavirus (NEC)	All jurisdictions
Ornithosis‡‡	All jurisdictions
Q fever	All jurisdictions except ACT
Other bacterial infections
Legionellosis	All jurisdictions
Leprosy	All jurisdictions
Meningococcal infection§§	All jurisdictions
Tuberculosis	All jurisdictions

* Unspecified hepatitis includes cases in whom the duration of infection could not be determined.

† In the Northern Territory and Queensland, includes incident hepatitis cases.

‡ Notified as 'foodborne disease' or 'gastroenteritis in an institution' in New South Wales.

§ Infection with Shiga-like toxin/verotoxin-producing Escherichia coli (SLTEC/VTEC).

|| Includes Chlamydia trachomatis identified from cervical, rectal, urine, urethral, throat and eye samples, except for South Australia which reports only genital tract specimens, the Northern Territory which excludes ocular specimens, and Western Australia which excludes ocular and perinatal infections.

¶ Laboratory confirmed influenza is not a notifiable disease in South Australia but reports are forwarded to NNDSS.

** Flavivirus (NEC) replaces Arbovirus (NEC) from 1 January 2004.

†† In the Australian Capital Territory, Murray Valley encephalitis virus and Kunjin are combined under Murray Valley encephalitis virus.

‡‡ In the Australian Capital Territory ornithosis is reported as Chlamydia not elsewhere classified.

§§ Only invasive meningococcal disease is nationally notifiable. However, New South Wales, the Australian Capital Territory and South Australia also report conjunctival cases.

NEC Not elsewhere classified.

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The national dataset included fields for unique record reference number; notifying state or territory; disease code; age; sex; Indigenous status; postcode of residence; date of onset of the disease; death, date of report to the state or territory health department and outbreak reference (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 was collected. While not included in the national dataset, additional information concerning mortality and specific health risk factors for some diseases was obtained from states and territories.

Notification rates for each notifiable disease were calculated using 2004 mid-year resident population supplied by the Australian Bureau of Statistics (Appendix 1). 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 indirect method of standardisation, with 2001 census data as the standard population.

The geographical distribution of selected diseases was mapped using MapInfo software. Maps were based on the postcode of residence of each patient aggregated to the appropriate Statistical Division ( Map 1). Rates for the different Statistical Divisions were ordered into six groups — the highest value, the lowest value above zero, those equal to zero, and the intermediate values sorted into three equal-sized groups. The Statistical Divisions in each of the two territories, the Australian Capital Territory and the Northern Territory were combined to calculate rates for each territory as a whole.

Information from communicable disease surveillance is disseminated through several avenues of communication. At the fortnightly teleconferences of the Communicable Diseases Network Australia the most up-to-date information on topics of interest to the network is provided. The Communicable Diseases Intelligence ( CDI) quarterly journal publishes surveillance data and reports of research studies on the epidemiology and control of various communicable diseases. The Communicable Diseases Australia website publishes disease surveillance summaries from the NNDSS. The annual report of the NNDSS, Australia's notifiable diseases status, provides yearly summaries of notifications.

Notes on interpretation

The present report is based on 2004 'finalised' data from each state and territory. States and territories transmitted data to NNDSS on average every other day, and the final dataset for the year was agreed upon in July 2005. The finalised annual dataset represents a snap shot of the year after duplicate records and incorrect or incomplete data have been removed. Therefore, totals in this report may vary slightly from the totals reported in CDI quarterly publications.

Analyses in this report were based on the date of disease onset in an attempt to estimate disease activity within the reporting period. Where the date of onset was not known however, the date of specimen collection or date of notification, whichever was earliest, was used. As considerable time may have lapsed between onset and diagnosis dates for hepatitis B (unspecified) and hepatitis C (unspecified), for these conditions the date of diagnosis, which is the earliest of specimen, notification or notification received dates supplied, was used.

Notified cases can only represent a proportion (the 'notified fraction') of the total incidence (Figure 1) and this has to be taken into account when interpreting NNDSS data. Moreover, the notified fraction varies by disease, by jurisdiction and by time.

Figure 1. Communicable diseases notification fraction

Methods of surveillance vary between states and territories, each having different requirements for notification by medical practitioners, laboratories and hospitals. Although there is a list of national notifiable diseases, some diseases are not yet notifiable in some jurisdictions (Table 1).

Changes in surveillance practices introduced in some jurisdictions and not in others are additional factors that make comparison of data across jurisdictions difficult. In this report, information obtained from states and territories on any changes in surveillance practices including screening practices, laboratory practices, and major disease control or prevention initiatives undertaken in 2004, was used to interpret data.

Postcode information usually reflects the residential location of the case, but this does not necessarily represent the place where the disease was acquired. As no personal identifiers are collected in NNDSS, duplication in reporting may occur if patients move from one jurisdiction to another and were notified in both.

The completeness of data* in this report is summarised in Appendix 3. The case's sex was complete in 99.7 per cent of notifications and date of birth in 99.8 per cent of notifications. In 2004, nationally, Indigenous status was complete in 46 per cent of notifications, and varied by jurisdiction. Indigenous status^† was complete for 92 per cent of data reported in the Northern Territory, 89 per cent in South Australia, 66 per cent in Western Australia and 52 per cent in Victoria. In the remaining jurisdictions, less than 50 per cent of data were complete for Indigenous status.

Data completeness on Indigenous status also varied by disease; in notifications of tuberculosis (TB), Haemophilus influenzae type b, meningococcal disease, infectious syphilis and hepatitis A were more than 90 per cent complete for Indigenous status, while in notifications of other diseases such as chlamydial infection and salmonellosis, data completeness was 41 per cent.

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Notes on case definitions

In this report each notifiable disease is introduced with a case definition, the 'CDNA case definition'. These case definitions were agreed upon by CDNA to be implemented nationally by January 2004.

CDNA case definitions are only intended for reporting to NNDSS. States and territories may have case definitions which reflect their local public health needs. These may be the same as or more comprehensive than the CDNA case definitions.

In 2004, not all jurisdictions implemented the CDNA case definitions ( Queensland did not implement the CDNA case definitions in 2004 and New South Wales introduced it in August 2004). This has to be kept in mind when comparing data across time and between jurisdictions.

Footnote:

* Definition of completeness = (Number with valid data/total notifications x 100.

† Data completeness = (Total notifications – Indigenous status 'Not stated or missing')/total notifications x 100.

'Indigenous status' is a variable defined by the following values:

1=Indigenous – (Aboriginal but not Torres Strait Islander origin)

2=Indigenous – (Torres Strait Islander but not Aboriginal origin)

3=Indigenous – (Aboriginal and Torres Strait Islander origin)

4=Not indigenous – ( not Aboriginal or Torres Strait Islander origin)

9=Not stated

Blank/missing/null=No information provided