Notes on interpretation

The present report is based on 2007 'finalised' data from each state or territory agreed upon in September 2008 and represents a snap shot of the year after duplicate records and incorrect or incomplete data were 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 diagnosis in an attempt to estimate disease activity within the reporting period. The date of diagnosis is the onset date or where the date of onset was not known, the earliest of the specimen collection date, the notification date, or the notification receive date. As considerable time may have elapsed between the onset and diagnosis dates for hepatitis B (unspecified), hepatitis C (unspecified) and tuberculosis, the earliest of specimen date, health professional notification date or public health unit notification receive date was used for these conditions.

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 notifiable fraction

Top of page

A survey of jurisdictional public health departments was conducted in 2005 to ascertain the source of each notification.¹¹ Notifications from Queensland were almost entirely supplied by laboratories (Table 2). In 3 other jurisdictions more than 90% of notifications originated from the laboratory. In 3 states almost half of the notifications were reported by both the doctor and laboratory. Only New South Wales, South Australia and Western Australia reported that greater than 15% of notifications in their jurisdictions originated from doctors only.

Table 2: Percentage of notifications from different sources, Australia, 2005, by state or territory

State or territory	Source of notifications
	Laboratory only	Doctor only	Laboratory and doctor
ACT	98	1	1
NSW	70–80	20–30	<1
NT	95	5	<1
Qld	99	1	<1
SA	24	17	59
Tas	95	5	<1
Vic	50	7	43
WA	27	15	58

Source: Oxenford, Chapter 3 Current practices surrounding reporting of notifiable diseases by laboratories to state and territory health departments.¹¹

Top of page

Methods of surveillance vary between states and territories, each having different requirements for notification by medical practitioners, laboratories and hospitals. Although the National Notifiable Diseases List² was established, some diseases are not yet notifiable in all 8 jurisdictions (Table 3).

Table 3: Diseases notified to the National Notifiable Diseases Surveillance System, Australia, 2007

Disease	Data received from
Bloodborne diseases
Hepatitis (NEC)	All jurisdictions
Hepatitis B (incident)	All jurisdictions
Hepatitis B (unspecified)*	All jurisdictions
Hepatitis C (incident)	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 unspecified duration*	All jurisdictions except South Australia
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 and Victoria
Varicella zoster (shingles)**	All jurisdictions except New South Wales and Victoria
Varicella zoster (unspecified)**	All jurisdictions except New South Wales and Victoria
Vectorborne diseases
Barmah Forest virus infection	All jurisdictions
Dengue virus infection	All jurisdictions
Flavivirus infection (NEC)††	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 infection§§	All jurisdictions
Tuberculosis	All jurisdictions

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

† In Queensland, includes incident hepatitis C cases.

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

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

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

¶ Laboratory confirmed influenza was not a notifiable disease in South Australia but reports were forwarded to the National Notifiable Diseases Surveillance System.

** Nationally notifiable from 2006 and first full year of national reporting from 2007.

†† Flavivirus (NEC) replaced Arbovirus (NEC) from 1 January 2004.

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

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

NEC Not elsewhere classified.

Top of page

Changes in surveillance practices may have been introduced in some jurisdictions and not in others, and makes the comparison of data across jurisdictions difficult. In this report, some information was obtained from states and territories, including changes in surveillance practices, screening practices, laboratory practices, and major disease control or prevention initiatives to assist in the interpretation of the 2007 data.

Postcode information usually reflects the residential location of the case, but this does not necessarily represent the place where the disease was acquired. In December 2008, the CDNA endorsed the NNDSS cross-border notification protocol, which determines that the jurisdiction of residence of a case has the responsibility of reporting the notification to NNDSS. This was implemented from 1 January 2009, and may also affect some retrospective notifications, including those reported in 2007, by removing duplicates and preventing the loss of notification data in NNDSS.

Data completeness was assessed for the notification's sex, age at onset, and indigenous status, and reported as the proportion of complete notifications. The completeness of data in this report is summarised in the Results.

The per cent data completeness was defined as:

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

The indigenous status was defined by the following nationally accepted values:¹²

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, unknown

Notes on cases definitions

Each notifiable disease is governed by a national surveillance case definition for reporting to NNDSS. These case definitions were agreed by CDNA and implemented nationally from January 2004 and were used by all jurisdictions for the first time in 2005. The national surveillance case definitions and their status are available from http://www.health.gov.au/casedefinitions