This article {extract} was published in Communicable Diseases Intelligence Vol 29 No 1 March 2005 and may be downloaded as a full version PDF from the Table of contents page.
Results, continued
Bloodborne diseases
In 2002, bloodborne viruses reported to the NNDSS included hepatitis B, C, and D. Human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) diagnoses are reported directly to the National Centre in HIV Epidemiology and Clinical Research (NCHECR). Information on national HIV/AIDS surveillance can be obtained through the NCHECR website at www.med.unsw.edu.au/nchecr.
When reported to NNDSS, newly acquired hepatitis C and hepatitis B infections (incident) were differentiated from those where the timing of disease acquisition was unknown (unspecified). As considerable time may have elapsed between onset and report date for chronic hepatitis infections, the analysis of unspecified hepatitis B and unspecified hepatitis C infections in the following sections is by report date, rather than by onset date.
Hepatitis B
Incident hepatitis B notifications
Since 1995, all jurisdictions have reported incident cases of hepatitis B to the NNDSS. The rate of incident hepatitis B notifications between 1994 and 2000 ranges around 1-2 cases per 100,000 population (Figure 5). In total, 400 incident cases were reported to the NNDSS with an onset date in 2002, giving a national notification rate of 2.0 cases per 100,000 population for this year. In 2002, the highest rates were reported from the Northern Territory (5.1 cases per 100,000 population) and Tasmania (4.0 cases per 100,000 population).
Figure 5. Trends in notification rates of incident and unspecified hepatitis B infections, Australia, 1995 to 2002
The highest rates of incident hepatitis B notifications were in the 30-34 year age group for males and the 20-24 year age group for females (Figure 6). The highest notification rate for men was 7.6 cases per 100,000 population, while the highest notification rate for women was 4.8 cases per 100,000 population. Overall, infections in males exceeded those in females, with a male to female ratio of 1.9:1.
Figure 6. Notification rate for incident hepatitis B infections, Australia, 2002, by age group and sex
Trends in the age distribution of incident hepatitis B infections are shown in Figure 7. Rates in children aged 0-14 years and adults over 40 years have remained relatively stable . The increase in rates of incident hepatitis B in the 20-29 year age range was reversed in 2002 with the first decline in rates since 1996. Declines in rates continued in 2002 in the 15-19 year age group, while the rate of increase in the 30-39 year age range slowed.
Figure 7. Trends in notification rates of incident hepatitis B infections, Australia, 1995 to 2002, by age group
Risk factor information for incident hepatitis B virus infection was available from all states and territories except New South Wales, Western Australia and Queensland (Table 5). There were no cases reported from Australian Capital Territory.
Table 5. Risk factors identified in notifications of incident hepatitis B virus infection, Australia, 2002, by reporting state or territory
Risk factor |
NT | SA | Tas | Vic |
|---|---|---|---|---|
| Injecting drug use | 3 |
1 |
9 |
87 |
| Sexual contact with hepatitis B case | 0 |
3 |
3 |
48 |
| Household/other contact with hepatitis B | 1 |
1 |
0 |
11 |
| Overseas travel | 0 |
1 |
0 |
6 |
| Other risk factors | 2 |
1 |
2 |
3 |
| No risk factors identified | 1 |
4 |
3 |
20 |
| No information available | 3 |
0 |
2 |
0 |
| Total | 10 |
11 |
19 |
175 |
Unspecified hepatitis B notifications
Hepatitis B notifications have been reported to the NNDSS since 1991 by all jurisdictions except the Northern Territory, with unspecified cases separately notified from incident cases in most jurisdictions since 1994. The notification rate ranged from 20 to 40 cases per 100,000 population between 1991 and 2002 Figure 5. In 2002 there were 6,916 unspecified hepatitis B cases notified to NNDSS, a rate of 35.5 cases per 100,000 population. The male to female ratio for unspecified hepatitis B cases was 1.2:1. By jurisdiction, the highest rates of notification were in New South Wales (52.6 cases per 100,000 population) and Victoria (38.8 cases per 100,000 population). The highest rates were in the 35-39 year age group for men (75.3 cases per 100,000 population) and the 25-29 year age group for women (69.5 cases per 100,000 population) (Figure 8).
Figure 8. Notification rate for unspecified hepatitis B infections, Australia, 2002, by age group and sex*
* By report date.
Trends on the age distribution of unspecified hepatitis B infections are shown in Figure 9. There were declines in the rates in all age groups in 2002.
Figure 9. Trends in notification rates of incident hepatitis B infections, Australia, 1995 to 2002, by age group*
* By report date.
Infant hepatitis B immunisation was introduced in the Northern Territory in 1988 for Indigenous infants and then for all infants in this jurisdiction in 1990. Universal infant hepatitis B immunisation was introduced in the rest of Australia in May 2000. The effect of vaccination may take a number of years to be evident in childhood rates of hepatitis B infection. Vaccination coverage provided by the Australian Childhood Immunisation Register (ACIR) indicates approximately 95 per cent of infants are currently receiving hepatitis B vaccination in Australia.
There were 23 cases of unspecified hepatitis B infection in children in the 0-4 year age group reported from Western Australia, New South Wales, Victoria, South Australia, the Northern Territory and the Australian Capital Territory. Seven of these children were not vaccinated with hepatitis B vaccine and the vaccination status of the remainder was unknown.
Hepatitis C
Unspecified hepatitis C notifications
Hepatitis C infection has been notifiable in all Australian jurisdictions since 1995. While the rate of unspecified hepatitis C notifications has remained relatively stable since 1997 (Figure 10), 2001 represented the first year since 1997 where the number of notifications has decreased, a trend that was continued in 2002. Improved surveillance practice, such as better classification of incident cases and increased duplicate checking may account for some of the decrease in unspecified hepatitis C notifications. Whether the decrease represents the fact that there is a smaller pool of infected individuals who have not been previously diagnosed will only become more apparent over the next few years.
Figure 10. Trends in notification rates, incident and unspecified hepatitis C infection, Australia, 1995 to 2002
In 2002, there were 15,981 unspecified hepatitis C infections reported to NNDSS, a notification rate of 81.3 per 100,000 population. Of the total notifications of unspecified hepatitis C, 42 per cent of the notifications were from New South Wales, which also had the highest notification rate (100.5 cases per 100,000 population). The male to female ratio was 1.6:1. The highest reporting rates were in the 30-34 year age group for males (216.4 cases per 100,000 population), although there was little variation across the 29-44 year age range, from 203 to 269.1 cases per 1000,000 population. The highest notification rate for females (137.9 cases per 100,000 population) was in the 20-24 year age group (Figure 11).
Figure 11. Notification rate for unspecified hepatitis C infections, Australia, 2002, by age group and sex*
* By report date.
Trends on the age distribution of unspecified hepatitis C infections are shown in Figure 12. Overall, the highest rates were in the 20-39 year age range. Rates fell in the 15-39 year age range in 2002.
Figure 12. Trends in notification rates of unspecified hepatitis C infections, Australia, 1995 to 2002, by age group*
* By report date.
Incident hepatitis C notifications
Reporting of incident hepatitis C notifications from New South Wales and Western Australia commenced in 1993, from the Australian Capital Territory in 1994, from South Australia and Tasmania in 1995 and from Victoria in 1997. Incident hepatitis C cases are not differentiated from unspecified cases in notifications received from Queensland or the Northern Territory. As the introduction of reporting was staggered, for the purposes of this report, only cases from 1997 are included.
In total there were 434 incident cases of hepatitis C reported with an onset date in 2002, giving a rate of 2.8 cases per 100,000 population. While this represents a decrease in cases relative to 2001, these data should be interpreted with caution as the numbers may be affected by changes in surveillance practices. The proportion of all hepatitis C notifications that were known incident cases was 2.6 per cent in 2001. The highest rates of incident hepatitis C infection were reported from Western Australia (7.0 cases per 100,000 population). The highest rates of incident hepatitis C notifications were in the 20-24 year age group for females (9.6 per 100,000 population) and the 25-29 year age group for males (11.8 per 100,000 population) (Figure 13). Overall, the male to female ratio was 1.4:1.
Figure 13. Notification rate for incident hepatitis C infections, Australia, 2002, by age group and sex
Trends on the age distribution of incident hepatitis C infections are shown in Figure 14. While rates in the 0-14 and over 40 year age groups have remained stable , increases observed in the 15-39 year age range between 2000 and 2001 were reversed in 2002.
Figure 14. Trends in notification rates of incident hepatitis C infections, Australia, 1997 to 2002, by age group
Hepatitis D
Hepatitis D is a defective single-stranded RNA virus that requires the hepatitis B virus to replicate. Hepatitis D infection can be acquired either as a co-infection with hepatitis B or as a superinfection of persons with chronic hepatitis B infection. People co-infected with hepatitis B and hepatitis D may have more severe acute disease and a higher risk of fulminant hepatitis compared with those infected with hepatitis B alone. The modes of hepatitis D transmission are similar to those for other blood borne viruses, and in countries with a low hepatitis B prevalence, intravenous drug users are the main risk group.
There were 20 notifications of hepatitis D to the NNDSS in 2002 at a notification rate of 0.1 per 100,000 population. Of the 21 notifications, 10 were reported from New South Wales, 9 from Victoria, and 1 from Queensland. The majority (18/20, 90%) of cases were males, with the highest rate reported in the 20-24 year age group (0.6 cases per 100,000 population).
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Communicable Diseases Surveillance
This issue - Vol 28 No 1, March 2004
NNDSS Annual report 2003
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