This article {extract} was published in Communicable Diseases Intelligence Vol 31 No 1 March 2007 and may be downloaded as a full version PDF from the Table of contents page.

Results, continued

Bloodborne diseases

Bloodborne viruses reported to the NNDSS include 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 www.med.unsw.edu.au/nchecr

Hepatitis B

Incident hepatitis B notifications

Case definition – Hepatitis B (incident) Only confirmed cases are reported. Confirmed case: Detection of hepatitis B surface antigen (HBsAg) in a case shown to be negative within the last 24 months, OR detection of hepatitis HBsAg and IgM to hepatitis B core antigen in the absence of prior evidence of hepatitis B infection OR detection of hepatitis B virus by nucleic acid testing and IgM to hepatitis B core antigen in the absence of evidence of prior hepatitis B infection.

In 2005, 245 cases of incident hepatitis B infection were reported to NNDSS, giving a national notification rate of 1.2 cases per 100,000 population. The Northern Territory recorded the highest notification rate in 2005 with 2.5 cases per 100,000 population. Over the past 10 years, the rate of notification of incident hepatitis B infection increased from 1.5 cases per 100,000 population in 1996 to 2.2 cases per 100,000 population in 2002 and then declined to 1.2 cases per 100,000 population in 2005 (Figure 5).

Figure 5. Notification rate of incident hepatitis B and hepatitis B (unspecified), Australia, 1995–2005, by year*

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

In 2005, the 35–39 year age group among males (4.4 cases per 100,000 population) had the highest rate of incident hepatitis B infection whereas the 25–29 year age group had the highest notification rate (3.1 cases per 100,000 population) (Figure 6) among females. Notifications of incident hepatitis B infection in males exceeded those in females, with a male to female ratio of 1.8:1 in 2005.

Figure 6. Notification rate of incident hepatitis B infections, Australia, 2005, by age group and sex

Trends in incident hepatitis B infection by year and age group are shown in Figure 7. In 2001–2005, the notification rate of incident hepatitis B fell by 81% among cases in the 15–19 year age group, and by 58% among cases in the 20–29 year age group. Increased adolescent vaccine coverage may have played a role in this reduction.

Figure 7. Notification rate of incident hepatitis B infections, Australia, 1995 to 2005, by year and age group

The source of exposure for cases of incident hepatitis B infection in 2005 was reported from South Australia, Victoria and the Australian Capital Territory (Table 5). In 2002–2005, the proportion of notifications of newly-acquired hepatitis B infection associated with injecting drug use, or heterosexual contact only, remained relatively stable at around 45%–50% and 21%–22%, respectively. The proportion of notifications of newly-acquired hepatitis B infections with an undetermined source of exposure to hepatitis B virus (HBV) declined from 23% in 2002 to 15% in 2005.

Table 5. Incident hepatitis B infection, Australia,* 2005, by exposure category

Exposure category	Number	Percentage
Injecting drug use	45	46
Sexual contact	33	34
Male homosexual contact	7	21
Heterosexual contact	22	67
Not specified	4	12
Blood/tissue recipient	0	0
Skin penetration procedure	1	1
Healthcare exposure	0	0
Household contact	3	3
Other	1	1
Undetermined	15	15
Total	98	100

Source: National Centre in HIV Epidemiology and Clinical Research 2006.²

* Data from South Australia, Victoria and the Australian Capital Territory only.

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Hepatitis B (unspecified) notifications

Case definition – Hepatitis B – unspecified Only confirmed cases are reported. Confirmed case: Detection of hepatitis B surface antigen or hepatitis B virus by nucleic acid testing in a case who does not meet any of the criteria for a newly acquired case.

In 2005, a total of 6,396 cases of hepatitis B (unspecified) infection were notified to NNDSS, giving a rate of 31.5 cases per 100,000 population. The Northern Territory (98.1 cases per 100,000 population), New South Wales (40.0 cases per 100,000 population) and Victoria (33.4 cases per 100,000 population) recorded the highest notification rates. The male to female ratio was 1.7:1. Among males, the highest notification rate was in the 25–29, 30–34 and the 35 –39 year age groups (65.0 cases per 100,000 population), whereas among females, the highest notification rate was in the 25–29 year age group (77.0 cases per 100,000 population, Figure 8).

Figure 8. Notification rate of hepatitis B (unspecified) infections, Australia, 2005, by age group and sex

Notifications of hepatitis B infection (unspecified) increased from 19.4 in 1996 to 42.8 in 2000 and then declined to around 29 cases per 100,000 population in 2003–2005 (Figure 5). Trends in hepatitis B (unspecified) infection by age group and year are shown in Figure 9. In 2005, rates of hepatitis B (unspecified) notifications remained stable compared to 2003 and 2004 rates. There were marginal increases in the 15–19 and 20–29 year age groups by 22% and 17%, respectively.

Figure 9. Notification rate of hepatitis B (unspecified) infections, Australia, 1995 to 2005, by year and age group

In 2005, 36 cases of HBV (1 incident and 35 unspecified) infection in children in the 0–4 year age group were reported. Approximately 95% of infants born in Australia in 2005 received hepatitis B vaccination (http://www.ncirs.usyd.edu.au, 2006).

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Hepatitis C

Incident hepatitis C notifications

Case definition – Hepatitis C (newly acquired - incident) Only confirmed cases are reported. Confirmed case: Requires detection of anti-hepatitis C antibody or detection of hepatitis C virus in a case with a negative test recorded in the last 24 months OR Detection of anti-hepatitis C antibody in a case aged 18 to 24 months or detection of hepatitis C virus in a case aged 1 to 24 months OR detection of anti-hepatitis C antibody or hepatitis C virus AND clinical hepatitis within the last 24 months (defined as jaundice, urine bilirubin or ALT seven times the upper limit of normal) where other causes of acute hepatitis have been excluded.

A total of 357 incident cases of hepatitis C with an onset date in 2005 were notified, giving a notification rate of 1.8 cases per 100,000 population (Figure 10). The proportion of all hepatitis C notifications in 2005 that were documented as incident cases was 3%. The highest rate of incident hepatitis C infection was reported from Tasmania and Western Australia (5.2 cases per 100,000 population).

Figure 10. Notification rates for hepatitis C infections (incident and unspecified), Australia, 1995 to 2005

In 2005, the highest rate of incident hepatitis C notification was in the 25–29 age group in males (7.7 cases per 100,000 population) and in the 20–24 and 25–29 age groups in females (5.2 cases per 100,000 population) (Figure 11).

Figure 11. Notification rate of incident hepatitis C infections, Australia, 2005, by age group and sex

Trends in the age distribution of incident hepatitis C infection are shown in Figure 12. In 2001–2005, notification rates declined by 56% in the 15–19 year age group, by 51% in the 20–29 year age range and by 43% in the 30–39 year age range.

Figure 12. Notification rate of incident hepatitis C infections, Australia, 1997 to 2005, by year and age group

The exposure history of cases of incident hepatitis C was collected in the Australian Capital Territory, South Australia, Victoria and Western Australia in 2005 (Table 6). At least 65% of incident hepatitis C infections were among people with a history of injecting drug use.

Table 6. Incident hepatitis C infection, Australia,* 2005, by exposure category

Exposure category	Number	Percentage
Injecting drug use	261	62.3
Sexual contact	11	2.6
Blood/tissue recipient	1	0.2
Skin penetration procedure	7	1.7
Healthcare exposure	1	0.2
Household contact	3	0.7
Other	18	4.3
Undetermined	117	27.9
Total	419	100.0

* Data from the Australian Capital Territory, South Australia, Tasmania, Victoria and Western Australia only, (NCHECR, 20062).

A total of 9,700 cases (range 6,600–13,200 cases) of incident hepatitis C infection were estimated to have occurred in Australia in 2005.3 This means that one in 27 incident cases (range 1 in 18 to 1 in 37 cases) had been notified.

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Hepatitis C (unspecified) notifications

Case definition – Hepatitis C (unspecified) Only confirmed cases are reported. Confirmed case: Requires detection of anti-hepatitis C antibody or detection of hepatitis C virus in a case who does not meet any of the criteria for a newly acquired case and is aged more than 24 months.

In 2005, 12,250 hepatitis C (unspecified) infections were notified to NNDSS, giving a notification rate of 64.6 cases per 100,000 population. The national notification rate for hepatitis C (unspecified) infection declined from 104 cases per 100,000 population in 2000 to 64.6 cases per 100,000 population in 2005 (Figure 10). Improved surveillance practice, such as better classification of incident cases and increased duplicate checking, may account for some of the decrease in hepatitis C (unspecified) notifications.

In 2005, the Northern Territory continued to have the highest notification rate (125.3 cases per 100,000 population). Nationally, the male to female ratio was 1.7:1. The highest notification rates occurred in the age groups 25–29, 30–34 and 35–39 year age groups (166.3 cases per 100,000 population) among males and in the 25–29 year age group (103.9 cases per 100,000 population) among females (Figure 13).

Figure 13. Notification rate of hepatitis C (unspecified) infections, Australia, 2005, by age group and sex

Trends in the age distribution of hepatitis C (unspecified) infection are shown in Figure 14. Between 2000 and 2005, the notification rates of hepatitis C (unspecified) among the 15–19 year age group decreased on average by 19% per year, and in 2005 it decreased by 38%. Notification rates also fell by 4% per year in the same period (2000 to 2005) among cases in the 20–29 year age group and by 32% in 2005. Rates in the other age groups remained relatively stable during this period. The decline in the rate of notification of hepatitis C infection may be attributable to a reduction in risk behaviour related to drug injecting among young people, but changes in the rates of testing may also have contributed to the decline.

Figure 14. Notification rate of hepatitis C (unspecified) infection, Australia, 1995 to 2005, by age group

In 2005, an estimated 197,300 people were living in Australia with chronic hepatitis C infection, of which 153,900 had early liver disease (Stage 0/1); 38,100 had moderate liver disease (Stage 2/3); and 5,300 were living with hepatitis C related cirrhosis.³

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Hepatitis D

Case definition – Hepatitis D Only confirmed cases are reported. Confirmed case: Detection of IgM or IgG antibodies to hepatitis D virus or detection of hepatitis D on liver biopsy in a case known to be hepatitis B surface antigen positive.

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 super-infection 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 30 notifications of hepatitis D to the NNDSS in 2005 giving a notification rate of 0.2 cases per 100,000 population. The male to female ratio was 2.4:1. Of the 30 notifications, 15 were reported from New South Wales, 11 from Queensland and 2 each from Victoria and Western Australia.