This article {extract} was published in Communicable Diseases Intelligence Vol 34 No 3 September 2010 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 NCHECR. Information on national HIV/AIDS surveillance can be obtained through the NCHECR web site at www.nchecr.unsw.edu.au
Hepatitis B
Hepatitis B notifications are classified as either 'newly acquired' (infection acquired within 24 months prior to diagnosis) or 'unspecified' (infection acquired greater than 24 months prior to diagnosis or not able to be specified). The classification of hepatitis B cases is primarily based on serological evidence or evidence of a previously negative test within the 24 months prior to diagnosis. In 2008, there were 6,845 notifications of hepatitis B (both newly acquired and unspecified), corresponding to a rate of 31.9 notifications per 100,000 population. Following a peak of notifications between 2000 to 2001 (42.5 and 43.0 per 100,000 population, respectively), the overall hepatitis B notification rate has declined and remained stable at around 32 notifications per 100,000 population between 2003 and 2008. In 2008, the Northern Territory recorded the highest rate of hepatitis B notifications at 93.3 per 100,000 population, followed by New South Wales (37.2 per 100,000 population) and Victoria (36.1 per 100,000 population).
Since the introduction of the adolescent hepatitis B vaccination program for children aged between 10 and 13 years in 1997,11 there has been a general decline in overall hepatitis B notification rates amongst the 15–19 and 20–29 year age groups. In 2008, 2 notifications of newly acquired hepatitis B and 24 notifications of hepatitis B (unspecified) were reported in children in the 0–4 year age group, representing 0.8% and 0.4% of hepatitis notifications in these categories respectively. Approximately 93% of the 2008 Australian birth cohort received the full-course of the hepatitis B vaccine.9, 12–14
Newly acquired hepatitis B notifications
In 2008, 245 newly acquired hepatitis B notifications (1.1 per 100,000 population) were reported to NNDSS, which was lower than in 2007 (294 notifications; 1.4 per 100,000 population). The 2008 notification rate was the lowest identified over the past 10 years, following a peak of 2.1 notifications per 100,000 population between 2000 and 2001 (Figure 4).
Figure 4: Notification rate for newly acquired hepatitis B* and unspecified hepatitis B,† Australia, 1998 to 2008, by year‡
* Data for newly acquired hepatitis B for the Northern Territory (1998–2004) includes some unspecified hepatitis B cases.
† Data for unspecified hepatitis B for all jurisdictions except the Northern Territory between 1998 and 2004.
‡ Year of diagnosis for newly acquired hepatitis B and for hepatitis B (unspecified) notifications, and not necessarily year of infection.
Nationally, the proportion of all hepatitis B notifications in 2008 that were documented as newly acquired cases was 3.6%, compared with 4.1% in 2007. The proportion of newly acquired infections compared to total hepatitis B infections varied substantially – Tasmania (17%); Queensland, Victoria and Western Australia (5%); the Northern Territory (4%); South Australia (3%); and the Australia Capital Territory and New South Wales (2%). The highest rates of newly acquired hepatitis B infection were reported from the Northern Territory with 3.6 per 100,000 population and Tasmania (2.4 per 100,000 population). The identification and classification of newly acquired hepatitis B is reliant upon public health follow-up, and the level at which this occurs varies between jurisdictions and over time.
Trends for newly acquired hepatitis B infection by year and age group are shown in Figure 5. Between 2000 and 2008, the notification rate of newly acquired hepatitis B fell by 85% in the 15–19 year age group. In the 20–29 year age group, there was a steady decline of 66% following a peak of 7.2 notifications per 100,000 population in 2001. The trends in these age groups were seen for both sexes.
Figure 5: Notification rate of newly acquired hepatitis B,* Australia, 1998 to 2008, by year and age group
* Data for newly acquired hepatitis B for the Northern Territory (1998–2004) includes some unspecified hepatitis B cases.
In 2008, the highest notification rate of newly acquired hepatitis B infection was observed in the 25–29 and 30–34 year age groups amongst males (4.3 per 100,000 population each). Among females, the highest notification rate was in the 20–24 year age group (2.3 per 100,000 population) (Figure 6). Notifications of newly acquired hepatitis B infection were higher amongst males, with a male to female ratio of 2.2:1.
Figure 6: Notification rate for newly acquired hepatitis B, Australia, 2008, by age group and sex
In 2008, the exposure history for notifications of newly acquired hepatitis B was collected by health authorities in South Australia, Tasmania and Victoria and reported to the NCHECR. From 2003 to 2008, approximately half of the annual newly acquired hepatitis B notifications reported injecting drug use. The proportion of diagnoses reporting a history of heterosexual contact with a hepatitis B positive partner decreased from 21% in 2004 to 11% in 2006 and increased to 18% in 2008. The source of exposure to hepatitis B was undetermined in around 20% of cases.4
Unspecified hepatitis B notifications
In 2008, a total of 6,600 notifications of unspecified hepatitis B infection were reported to the NNDSS, compared with 6,887 notifications in 2007. The Northern Territory recorded the highest notification rate (89.6 per 100,000 population), compared with other jurisdictions such as New South Wales (36.6 per 100,000 population) and Victoria (34.5 per 100,000 population).
In 2008, sex was recorded in 6,528 of the 6,600 notifications (99%). The male to female ratio of notifications was 1.2:1. Among males, the highest notification rate was amongst the 30–34 year age group (64.3 per 100,000 population) followed by the 35–39 and 25–29 year age groups with rates of 60.8 and 59.8 per 100,000 population respectively. Among females, the highest notification rate was amongst the 25–29 year age group (73.3 per 100,000 population), followed by the 30–34 year age group (67.6 notifications per 100,000 population) (Figure 7).
Figure 7: Notification rate for unspecified hepatitis B, Australia, 2008, by age group and sex*
* Excluding 72 cases whose sex or age were not reported.
The notification rates of hepatitis B (unspecified) have generally declined over the past 10 years, despite a peak of 41.3 notifications per 100,000 population in 2001 and a low point of 29.0 per 100,000 population in 2004 (Figure 4). In 2008, the rate of hepatitis B (unspecified) notifications (30.8 per 100,000) was approximately the same as those for 2005–2007 (range 30.2–32.7 per 100,000 population).
Trends in hepatitis B (unspecified) infection by age group, sex and year are shown in Figure 8. Rates across most age groups decreased in 2008, compared with 2007, with the 15–19 year age group declining by 11.8% (22.1 to 19.5 notifications per 100,000 population). The highest notification rates were amongst the 25–29 and 30–34 year age groups (67.4 and 66.7 per 100,000 population respectively).
Figure 8: Notification rate for unspecified hepatitis B,* Australia, 1998 to 2008, by year and age group
* Data for hepatitis B (unspecified) from all states except the Northern Territory between 1998 and 2004.
Hepatitis C
Hepatitis C notifications are classified as either 'newly acquired' (infection acquired within 24 months prior to diagnosis) or 'unspecified' (infection acquired greater than 24 months prior to diagnosis or not able to be specified). Current testing methods cannot distinguish between newly acquired (incident) and chronic infections (greater than 2 years or unspecified). The identification of newly acquired cases is therefore dependent on evidence of a previously negative test result within 24 months prior to their diagnosis (i.e. seroconversion). Ascertainment of hepatitis C testing histories usually requires active follow-up by public health units.
From 1999 to 2008, total hepatitis C notification rates declined by 51.2% (108.3 to 52.8 notifications per 100,000 population). The greatest reductions were between 2001 and 2002 (20% decline), and are believed to be associated with the detection and accounting of prevalent cases that occurred in the late 1990s through the expansion of testing in high risk groups15 (Figure 9). The continuing decline in the notification rate may be attributable to reductions in the prevalence of injecting drug use, and risk behaviours related to injecting practices, especially amongst young people, and the implementation of needle exchange programs.4,15 Changes in hepatitis C laboratory testing practices may have also contributed to the observed decline.
Figure 9: Notification rates for newly acquired hepatitis C* and unspecified hepatitis C,† Australia, 1998 to 2008
* Data for newly acquired hepatitis C from all states and territories except Queensland 1998–2008 and the Northern Territory 1998–2004.
† Data for unspecified hepatitis C provided from Queensland (1998–2008) and the Northern Territory (1998–2004) include both newly acquired and unspecified hepatitis C notifications.
Newly acquired hepatitis C notifications
Notifications of newly acquired hepatitis C were received from all jurisdictions except Queensland, where all cases of hepatitis C, regardless of whether they are newly acquired, are reported as unspecified hepatitis C. There were 381 newly acquired hepatitis C notifications reported in 2008 (385 notifications in 2007), giving a notification rate of 2.2 per 100,000 population (Figure 9).
Figure 10: Notification rate for newly acquired hepatitis C, Australia,* 2008, by age group and sex†
* Data from all states and territories except Queensland.
† Excludes 1 case whose sex was not reported.
As a proportion of all hepatitis C notifications in 2008, 3.4% were identified as newly acquired infections, compared with 3.1% in 2007. Amongst jurisdictions, the proportion of newly acquired infections compared with total hepatitis C infections varied substantially – South Australia (11%), Western Australia (8%), Tasmania (7%), Victoria (6%), the Australia Capital Territory and the Northern Territory (3%), and New South Wales (1%). The highest rates of newly acquired hepatitis C infection were reported in Tasmania (4.8 per 100,000 population), Western Australia (4.7 per 100,000 population) and South Australia (4.1 per 100,000 population). The identification and classification of newly acquired hepatitis C is reliant upon public health follow-up to identify testing and clinical histories. The level of case follow-up and method varies among jurisdictions.
Notification rates of newly acquired hepatitis C were highest in males in the 25–29 and 20–24 year age groups (11.1 and 8.8 per 100,000 population respectively), with peaks in females also occurring for the same 5 year age groups (6.2 and 5.7 per 100,000 population respectively) (Figure 10).
Trends in the age distribution of newly acquired hepatitis C infection are shown in Figure 11. While rates for individual age groups can vary markedly from year to year, there is a general downward trend in the 15–19 and 20–29 year age groups. Overall, the annual rates in the other age groups are similar to trends in previous years.
Figure 11: Notification rate for newly acquired hepatitis C, Australia,* 1998 to 2008, by age group and year
* Data from all states and territories except Queensland (1998–2008) and the Northern Territory (1998–2004).
Enhanced surveillance data for newly acquired infections in 2008 were collected in all jurisdictions except Queensland. Of the newly acquired hepatitis C notifications within these jurisdictions, 88% had exposure history information recorded (335 of 381) (Table 10). Approximately 78% of these hepatitis cases were amongst people with a history of injecting drug use (45% with injecting drug use in the 24 months prior to diagnosis), and 25% were amongst persons detained in a correctional facility within the 24 months prior to their diagnosis. Screening rates are higher in the prison entry population than the general population. A screening survey of prison entrants conducted over a 2-week period in 2007 found that the prevalence of hepatitis C, based on hepatitis C antibody detection, was 35% amongst this population.16
Table 10: Newly acquired hepatitis C notifications, selected jurisdictions,* 2008, by sex and exposure category in the 24 months prior to diagnosis
Exposure category |
Number of exposure factors reported | Percentage§ of total cases|| (n = 335) | ||
|---|---|---|---|---|
| Male | Female | Total‡ | ||
| Injecting drug use | 95 |
54 |
150 |
44.8 |
| Imprisonment | 72 |
12 |
84 |
25.1 |
| Skin penetration procedure | 50 |
39 |
89 |
26.6 |
| Tattoos | 35 |
19 |
54 |
16.1 |
| Ear or body piercing | 14 |
18 |
32 |
9.6 |
| Acupuncture | 1 |
2 |
3 |
0.9 |
| Healthcare exposure | 6 |
10 |
16 |
4.8 |
| Surgical work | 5 |
5 |
10 |
3.0 |
| Major dental surgery | 1 |
4 |
5 |
1.5 |
| Blood/tissue recipient | 0 |
1 |
1 |
0.3 |
| Sexual contact | 15 |
25 |
40 |
11.9 |
| Household contact | 11 |
9 |
20 |
6.0 |
| Needlestick or biohazardous injury¶ | 3 |
3 |
6 |
1.8 |
| Other | 3 |
3 |
6 |
1.8 |
| Risk factor unable to be determined | 4 |
3 |
7 |
2.1 |
| Total number of exposure factors reported† | 259 |
158 |
418 |
– |
* Includes diagnoses in the Australian Capital Territory, New South Wales, South Australia, Tasmania, Victoria, Western Australia and the Northern Territory.
† More than 1 exposure category for each case could be recorded.
‡ Total includes notifications in cases whose sex was not reported.
§ The denominator used to calculate the percentage is based on the total number of cases with exposure information recorded and as more than 1 exposure category for each case could be recorded, the total percentage does not equate to 100%.
|| Total number of cases where exposure history reported.
¶ Includes both occupational and non-occupational exposures.
Unspecified hepatitis C notifications
In 2008, 10,938 unspecified hepatitis C infections were notified to the NNDSS (51.0 notifications per 100,000 population) compared with 11,905 notifications in 2007 (56.5 notifications per 100,000 population).
The national notification rate for unspecified hepatitis C infection declined from 105.8 per 100,000 population in 1999 to 51.0 per 100,000 population in 2008 (Figure 9). Changes in surveillance practices; increased duplicate notification checks; changes in rates of testing; and the Northern Territory separately reporting newly acquired hepatitis C notifications from 2003, may account for some of the decrease in unspecified hepatitis C notifications since 2000, in addition to broader reductions in the prevalence of injecting drug use.4,15
In 2008, the Northern Territory continued to have the highest notification rate (101.0 per 100,000 population) followed by Tasmania (65.1 per 100,000 population), Western Australia (57.2 per 100,000 population) and the Australian Capital Territory (56.4 per 100,000 population). Queensland's rate was also high, at 61.3 per 100,000 population, however this included both newly acquired and unspecified cases.
The male to female ratio remained consistent with historical trends at 1.7:1. The highest notification rate occurred in the 30–34 year age group (136.0 per 100,000 population) amongst males and in the 25–29 and 30–34 year age groups (79.4 and 78.2 per 100,000 population respectively) amongst females (Figure 12).
Figure 12: Notification rate for unspecified hepatitis C,* Australia, 2008, by age group and sex†
* Data provided from Queensland includes both newly acquired and unspecified hepatitis C notifications.
† Excludes 38 cases whose sex was not reported.
Trends in the age distribution of unspecified hepatitis C infection are shown in Figure 13. From 2001 to 2008, the notification rates of unspecified hepatitis C declined by 79% amongst the 15–19 year age group, by 62% amongst the 20–29 year age group and by 49% in the 30–39 year age group. Trends in the 0–4 and the 40 years and over age groups have remained relatively stable over the past 10 years.
Figure 13: Notification rate for unspecified hepatitis C,* Australia, 1998 to 2008, by age group
* Data provided from Queensland (1998–2008) and the Northern Territory (1998–2004) include both newly acquired and unspecified hepatitis C notifications.
Although initial infection with the hepatitis C virus is asymptomatic or mildly symptomatic in more than 90% of cases, approximately 50%–80% of cases will go on to develop a chronic infection. Of those who develop a chronic infection, half will eventually develop cirrhosis or cancer of the liver.17 In 2008, it was estimated that 284,000 people living in Australia had been exposed to the hepatitis C virus. Of these, approximately 162,000 had chronic hepatitis C infection and early liver disease, and 44,000 had chronic hepatitis C infection and moderate liver disease associated with chronic hepatitis C infection; 5,700 were living with hepatitis C related cirrhosis; and 72,100 had cleared their infection.4
Hepatitis D
Hepatitis D is a defective single-stranded RNA virus that requires the presence of the hepatitis B virus to replicate. Hepatitis D infection can occur either as a co-infection with hepatitis B or as a super-infection with chronic hepatitis B infection.17 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 group at risk for hepatitis D.
In Australia, the rate of hepatitis D remains low. In 2008, there were 42 notifications of hepatitis D, compared with 34 notifications in 2007, giving a notification rate of 0.2 per 100,000 population. The male to female ratio was 4.3:1. Of the 42 notifications, 14 were reported from New South Wales, 13 from Victoria, 7 from Queensland, 6 from Western Australia and 1 case from the Northern Territory.
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Communicable Diseases Surveillance
This issue - Vol 34 No 3, September 2010
NNDSS Annual report 2008
Communicable Diseases Intelligence