NNDSS Annual Report Writing Group

Abstract

In 2012, 65 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 243,822 notifications of communicable diseases to the National Notifiable Diseases Surveillance System, an increase of 2% on the number of notifications in 2011. In 2012, the most frequently notified diseases were sexually transmissible infections (99,250 notifications, 40.7% of total notifications), vaccine preventable diseases (85,810 notifications, 35.2% of total notifications), and gastrointestinal diseases (31,155 notifications, 12.8% of total notifications). There were 16,846 notifications of bloodborne diseases; 8,305 notifications of vectorborne diseases; 1,924 notifications of other bacterial infections; 578 notifications of zoonoses; and 5 notifications of quarantinable diseases. Commun Dis Intell 2015;39(1):E46–E136.

Keywords: Australia, communicable diseases, epidemiology, surveillance

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Introduction

Australia’s notifiable diseases status, 2012, is an annual surveillance report of nationally notifiable communicable diseases. Communicable disease surveillance in Australia operates at the national, jurisdictional and local levels. Primary responsibility for public health action lies with the state and territory health departments. The role of communicable disease surveillance at the national level includes:

• identifying national trends;
• providing guidance for policy development and resource allocation at the national level;
• monitoring the need for and impact of national disease control programs;
• coordinating the response to national or multi-jurisdictional outbreaks;
• describing 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
• supporting quarantine activities, which are the responsibility of the Commonwealth government.

Information on communicable diseases surveillance is communicated through several means. The most up-to-date information on topics of interest is provided at the fortnightly teleconferences of the Communicable Diseases Network Australia (CDNA). A summary of these reports is available online from the Department of Health web site (http://www1.health.gov.au/internet/main/publishing.nsf/Content/cdnareport.htm).

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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 signed by Health Ministers in April 2008, establishes the operational arrangements to formalise and enhance existing surveillance and reporting systems; an important objective of the Act. Under the Agreement, in 2012 states and territories forwarded de-identified notification data on the nationally agreed set of 65 communicable diseases to the Australian Government Department of Health for the purposes of national communicable disease surveillance, although not all 65 diseases were notifiable in each jurisdiction. Data were electronically updated daily from states and territories. The system was complemented by other surveillance systems, which provided information on various diseases, including four that are not reported through the National Notifiable Diseases Surveillance System (NNDSS): HIV, AIDS and the classical and variant forms of Creutzfeldt-Jakob disease (CJD).

Newly diagnosed HIV infection and AIDS were notifiable conditions in all states and territories in 2012. These 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

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

In 2012, 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 jurisdictional health department 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 pathology service authorised a report or a 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 agents detected, or 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). There was a continual process of improving the national consistency of communicable disease surveillance through the daily, fortnightly and quarterly reviews 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, donovanosis, gonococcal infection and syphilis < 2 years duration) were reported from states and territories to NNDSS. With the exception of hepatitis B and hepatitis C these enhanced data are not included in this report. These data, along with influenza enhanced data, are reported in individual annual reports. Additional information concerning mortality and specific health risk factors for some diseases were obtained from states and territories and included in this report.

Notification rates for each disease were calculated using the estimated 2012 mid-year resident population supplied by the Australian Bureau of Statistics (Appendix 1 and Appendix 2).⁶ 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 with 2006 census data as the standard population. All rates are represented as the rate per 100,000 population unless stated otherwise.

Direct age standardised notification rates, using the method described by the Australian Institute of Health and Welfare⁷ were calculated for Aboriginal and Torres Strait Islander and non-Indigenous notifications for relevant sexually transmissible infections (STIs) for jurisdictions that had Indigenous status data completed for more than 50% of notifications over the period from 2007 to 2012. Where the Indigenous status of a notification was not completed, these notifications were counted as non-Indigenous in the analyses. These data, however, should be interpreted with caution, as STI screening may occur predominately in specific high risk groups, including in remote Aboriginal and Torres Strait Islander populations. Recent studies have suggested that higher rates in Aboriginal and Torres Strait Islander populations may be attributable to higher prevalence and reinfection rates while others have suggested that it may be due to increased testing and contract tracing.⁸

In the national case definitions for chlamydial infection, gonococcal infection and syphilis, the mode of transmission cannot be inferred from the site of infection. Infections in children may be acquired perinatally (e.g. congenital chlamydia).⁹ Notifications of chlamydial, gonococcal and non-congenital syphilis infections were excluded from analysis of age and sex distribution where the case was aged less than 13 years and the infection was able to be determined as non-sexually acquired through enhanced surveillance data, where available.

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Notes on interpretation

This report is based on 2012 data from each state and territory, agreed upon in August 2013. It represents a snapshot of the data for the year after duplicate records and incorrect or incomplete data were removed. Totals in this report may vary slightly from the totals reported in CDI quarterly publications.

Analyses in this report are based on the date of diagnosis in an attempt to estimate disease activity within the reporting period, with the exception of syphilis in Queensland, which is reported by the notification received date. For most diseases the date of diagnosis is the onset date or where the date of onset was not known, the earliest of the following dates: specimen collection date, the notification date, or the notification receive date. In January 2014, the NSC redefined the diagnosis date methodology for hepatitis B (unspecified), hepatitis C (unspecified), leprosy, syphilis (unspecified) and tuberculosis. As a considerable amount of time can elapse between the initial infection, the onset of symptoms and the subsequent diagnosis, the diagnosis date for these 5 diseases is derived from the notification receive date. This new definition was applied retrospectively to all notifications of hepatitis B (unspecified), hepatitis C (unspecified), leprosy, syphilis (unspecified) and tuberculosis.

When referring to NNDSS notification data throughout this report, the terms ‘cases’, ‘notified cases’ and ‘notifications’ should be considered interchangeable. Notifications only represent a proportion (the ‘notified fraction’) of the total incidence of any disease (Figure 1). This needs to be taken into account when interpreting NNDSS data. Moreover, the notified fraction varies by disease, jurisdiction and over time.

Figure 1: Communicable diseases notifiable fraction

Text version of Figure 1 (TXT 1 KB)

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A survey of state and territory public health departments was conducted in 2013 to ascertain the source of each notification (Table 1). Whilst most jurisdictions collect laboratory notification data, the percentage of notifications attributed to doctor only and laboratory and doctor for each state and territory is based on estimates deduced from the data that are available. Only Western Australia and New South Wales maintain data on the source of notifications as being from laboratories and/or doctors.

Table 1: Percentage* of notifications from different sources, 2012, by state or territory

State or territory	Source of notifications
	Laboratory only	Doctor only	Laboratory and doctor
* Not all percentages add up to 100% due to other sources of notifications and/or incomplete data for laboratory and medical notification fields.
ACT	95.0	<1	~4.0
NSW	98.3	0.3	0.4
NT	98.0	0.7	1.3
Qld	99.5	0.2	0.2
SA	5.0	2.2	92.8
Tas.	98.0	<1.0	1.0
Vic.	38.0	5.0	52.0
WA	33.5	1.4	65.3

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Methods of surveillance vary between states and territories, each having different requirements for notification by medical practitioners, laboratories and hospitals. Some diseases are not notifiable in all 8 jurisdictions (Table 2).

Table 2: Diseases notified to the National Notifiable Diseases Surveillance System, Australia, 2012

Disease	Data received from
* Infection with Shiga toxin/verotoxin-producing Escherichia coli. NEC Not elsewhere classified.
Bloodborne diseases
Hepatitis B (newly acquired)	All jurisdictions
Hepatitis B (unspecified)	All jurisdictions
Hepatitis C (newly acquired)	All jurisdictions, except Queensland
Hepatitis C (unspecified)	All jurisdictions
Hepatitis D	All jurisdictions
Gastrointestinal diseases
Botulism	All jurisdictions
Campylobacteriosis	All jurisdictions, except New South Wales
Cryptosporidiosis	All jurisdictions
Haemolytic uraemic syndrome	All jurisdictions
Hepatitis A	All jurisdictions
Hepatitis E	All jurisdictions
Listeriosis	All jurisdictions
Salmonellosis	All jurisdictions
Shigellosis	All jurisdictions
STEC, VTEC*	All jurisdictions
Typhoid	All jurisdictions
Quarantinable diseases
Cholera	All jurisdictions
Highly pathogenic avian influenza in humans	All jurisdictions
Plague	All jurisdictions
Rabies	All jurisdictions
Severe acute respiratory syndrome	All jurisdictions
Smallpox	All jurisdictions
Viral haemorrhagic fever	All jurisdictions
Yellow fever	All jurisdictions
Sexually transmissible infections
Chlamydial infections	All jurisdictions
Donovanosis	All jurisdictions
Gonococcal infection	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
Varicella zoster (chickenpox)	All jurisdictions, except New South Wales
Varicella zoster (shingles)	All jurisdictions, except New South Wales
Varicella zoster (unspecified)	All jurisdictions, except New South Wales
Vectorborne diseases
Arbovirus infection (NEC)	All jurisdictions
Barmah Forest virus infection	All jurisdictions
Dengue virus infection	All jurisdictions
Japanese encephalitis virus infection	All jurisdictions
Kunjin virus infection	All jurisdictions
Malaria	All jurisdictions
Murray Valley encephalitis virus infection	All jurisdictions
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
Tularaemia	All jurisdictions
Other bacterial infections
Legionellosis	All jurisdictions
Leprosy	All jurisdictions
Meningococcal disease (invasive)	All jurisdictions
Tuberculosis	All jurisdictions

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Over time, changes in surveillance practices may have been made in some states and territories but not others. This must be taken into consideration when comparing data between jurisdictions. In this report, some additional information was obtained from states and territories, to assist in the interpretation of the 2012 data. These include changes in surveillance, screening and laboratory practices, and disease control and prevention initiatives.

Postcode information usually reflects the place of residence of the case. However, it does not necessarily represent the place where the infection was acquired.

Data completeness was assessed for the sex, age at onset, and Indigenous status fields, and reported as the proportion of complete notifications. The completeness of data in this report is summarised in the results.

The per cent of data completeness was defined as:

Per cent of data completeness = (total notifications – missing or unknown) / total notifications x 100

Indigenous status was defined by the following nationally accepted criteria:¹⁰

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

In interpreting STI notification data, it is important to note that changes in notifications over time may not solely reflect changes in disease prevalence as changes in screening programs,^11,12 the use of less invasive and more sensitive diagnostic tests¹³ and periodic public awareness campaigns¹⁴ may influence the number of notifications that occur over time. Rates for STIs are particularly susceptible to overall rates of testing, with low testing rates resulting in an underestimation of disease and increased testing potentially causing an increase in notifications.¹⁵ For some diseases, changes in surveillance practices may also need to be taken into account when interpreting national trends.

The differences in rates between females and males for STIs should be interpreted with caution, as rates of testing, symptom status, health care-seeking behaviours, and partner notification differ between the sexes.¹⁶

Notes on case definitions

Each notifiable disease is reported to the NNDSS in accordance with the national surveillance case definition. These were agreed by CDNA and implemented nationally in January 2004 and were used by all jurisdictions for the first time in 2005. They are reviewed by the Case Definitions Working Group as required.

The national surveillance case definitions and their review status are available from the Department of Health web site (http://www.health.gov.au/casedefinitions).

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