Megge Miller, Paul Roche, Keflemariam Yohannes, Jenean Spencer, Mark Bartlett, Julia Brotherton, Jenny Hutchinson, Martyn Kirk, Ann McDonald, Claire Vadjic

Bloodborne diseases

In 2003, bloodborne viruses reported to the NNDSS included hepatitis B, C and D. HIV and 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 http://www.med.unsw.edu.au/nchecr

When reported to NNDSS, newly acquired (incident) hepatitis B and hepatitis C infections 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 unspecified 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

In 2003, 337 incident hepatitis B infections were reported to the NNDSS, giving a national notification rate of 1.7 cases per 100,000 population. The highest rates were reported from the Northern Territory (7.6 cases per 100,000 population) and Victoria (3.0 cases per 100,000 population). In 1995–2003, the rate of notification of incident hepatitis B infection was around 1–2 cases per 100,000 population (Figure 5).

Figure 5. Trends in notification rates, incident and unspecified hepatitis B infection, Australia, 1995 to 2003*

* Year of onset for incident hepatitis B and year of report for unspecified hepatitis B notifications.

In 2003, the highest rate of incident hepatitis B infection was in the 3 0–34 year age group among males (7.7 cases per 100,0000 male population) and in the 20–24 year age group among females (3.8 cases per 100,000 female population, Figure 6). Overall, infections in males exceeded those in females, with a male to female ratio of 2:1.

Figure 6. Notification rate for incident hepatitis B infections, Australia, 2003, by age group and sex

Trends in incident hepatitis B infection by year and age group are shown in Figure 7. Rates of incident hepatitis B infection among people aged less than 15 years or 40 years and older remained low in 1995–2003. Rates of notification of incident hepatitis B infection in the 15–19 and 20–29 year age groups peaked in 2000 and 2000–2001 respectively. Rates in the 15–19 and 20–29 year age groups declined from 3.7 and 7.3 cases in 2001 to 2.5 and 4.2 cases in 2003, respectively while rates in the 30–39 year age group remained around three cases per 100,000 population in 2001–2003.

The increased rates in these age groups in 2000–2001 was attributed to increased hepatitis B transmission among injecting drug users in Victoria, followed by a decline in the prevalence of infections in 2002 and 2003 during a heroin ‘drought’ (Greg Dore, personal communication).

Figure 7. Trends in notification rates of incident hepatitis B infections, Australia, 1995 to 2003, by age group

Risk factor information for incident hepatitis B infection was available from all states and territories except New South Wales, Western Australia and Queensland (Table 5). No cases of incident hepatitis B infection were reported from the Australian Capital Territory.

Table 5. Risk exposures associated with incident hepatitis B infection, Australia, 2003, by reporting state or territory*

Risk factor	NT	SA	Tas	Vic
Injecting drug use	5	5	6	80
Sexual contact with hepatitis B case	1	1	0	66
Household/other contact with hepatitis B	0	0	0	0
Overseas travel	1	1	0	0
Other risk factors	1	0	0	0
No risk factors identified	7	3	4	1
Total	15	10	10	147

* There were no cases of incident hepatitis B infection notified in the Australian Capital Territory.

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Unspecified hepatitis B notifications

In 2003, 5,833 cases of unspecified hepatitis B infection were notified to NNDSS, giving a rate of 29.3 cases per 100,000 population. By jurisdiction, New South Wales (39.4 cases per 100,000 population) and Victoria (33.1 cases per 100,000 population) recorded the highest notification rates. The male to female ratio was 1.3:1. Among males, the highest notification rate was in the 35–39 year age group (63.1 cases per 100,000 population), whereas among females, the highest notification rate was in the 25–29 year age group (60.3 cases per 100,000 population, Figure 8). In 1995–2003, the rate of notification of unspecified hepatitis B infection ranged from 20 to 40 cases per 100,000 population (Figure 5).

Figure 8. Notification rate for unspecified hepatitis B infections, Australia, 2003, by age group and sex*

* By report date.

In 2003, 14 cases of unspecified hepatitis B infection in children in the 0–4 year age group were reported. Five children had been vaccinated for hepatitis B infection, one child had not been vaccinated and the vaccination status of the remainder was unknown. Approximately 95 per cent of infants born in 2003 received hepatitis B vaccination in Australia.¹

Trends in unspecified hepatitis B infection by age group and year are shown in Figure 9. Rates of notification of unspecified hepatitis B infection peaked in 2000–2001 in the age groups 15–19 and 20–29 years. This pattern was similar to that for incident hepatitis B infection (Figure 7). In 2000–2003, the notification rate declined substantially in all age groups except in the 0–14 year age group, which had the lowest notification rate.

Figure 9. Trends in notification rates of unspecified hepatitis B infections, Australia, 1995 to 2003, by age group*

* By report date.

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Hepatitis C

Incident hepatitis C notifications

A total of 460 incident cases of hepatitis C with an onset date in 2003 were notified, giving a rate of 2.3 cases per 100,000 population (Figure 10). The proportion of all hepatitis C notifications that were known incident cases was 3.1 per cent in 2003. The highest rate of incident hepatitis C infection was reported from Western Australia (7.3 cases per 100,000 population).

Figure 10. Trends in notification rates, incident and unspecified hepatitis C infection, Australia, 1995 to 2003

Incident hepatitis C notification rates fell from 3.8 cases per 100,000 population in 2001 to 2.3 cases per 100,000 population in 2003. The reasons for this decline are not clear, as notifications of incident hepatitis C are a small fraction of the true number of new infections, estimated to be 16,000 in 2001.²

In 2003, the highest rate of incident hepatitis C notification was in the 20–24 year age group for males (11.4 cases per 100,000 population) and females (7.1 cases per 100,000 population, Figure 11). Overall, the male to female ratio was 1.6:1.

Figure 11. Notification rate for incident hepatitis C infections, Australia, 2003, by age group and sex

Trends in the age distribution of incident hepatitis C infection are shown in Figure 12. In 1997–2003, the highest rates of notification of incident hepatitis C infection were in the age group 20–29 years and 15–19 years.

Figure 12. Trends in notification rates of incident hepatitis C infections, Australia, 1997 to 2003, by age group

Hepatitis C transmission in Australia continued to occur predominately among people with a recent history of injecting drug use. 2 More than 75 per cent of people with incident hepatitis C infection reported a history of injecting drug use. Modelling of hepatitis has estimated that in 2003, an estimated 181,000 people were living with hepatitis C infection in Australia, including 143,000 with chronic hepatitis C infection and early liver disease (stage 0/1), 31,000 with chronic hepatitis C and moderate liver disease (stage 2/3) and 7,500 with hepatitis C related cirrhosis. A further 61,000 had hepatitis C antibodies without chronic infection.²

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Unspecified hepatitis C notifications

National notification rates of unspecified hepatitis C infection ranged between 96 and 104 cases per 100,000 population in 1995–2001. The national rate declined to 81.3 in 2002 and to 71.3 per 100,000 in 2003 (Figure 10). 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.

In 2003, 14,169 unspecified hepatitis C infections were notified to NNDSS, giving a notification rate of 71.3 cases per 100,000 population. Of the total notifications of unspecified hepatitis C, 36 per cent were from New South Wales, but the Northern Territory had the highest notification rate (104.9 cases per 100,000 population). The male to female ratio was 1.7:1. The highest reporting rates were in the 25–29 year age group for both males (191.5 cases per 100,000 population), and females (115.1 cases per 100,000 population, Figure 13).

Figure 13. Notification rate for unspecified hepatitis C infections, Australia, 2003, by age group and sex*

* By report date.

Trends in the age distribution of unspecified hepatitis C infections are shown in Figure 14. Overall, the highest rates were in the 20–29 and 30–39 year age groups. In the age group 30–39 years, the rate of diagnosis of unspecified hepatitis C infection declined steadily in 1995–2003 whereas in the age groups, 15–19 years and 20–29 years, a steady decline occurred from 2000 to 2003.

Figure 14. Trends in notification rates of unspecified hepatitis C infections, Australia, 1995–2003, by age group*

* By report date.

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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 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 with hepatitis B alone. The modes of hepatitis D transmission are similar to those for hepatitis B, and in countries with low hepatitis B prevalence, injecting drug users are the main risk group for hepatitis D.

There were 26 notifications of hepatitis D to the NNDSS in 2003 giving a notification rate of 0.1 per 100,000 population. Of the 26 notifications, 12 were reported from New South Wales, 13 from Victoria, and one from Queensland. The majority (22/26, 85%) of cases were males, with the highest rate reported in 40–44 and 45–49 year olds (0.6 cases per 100,000 population).

 

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.