This article was published in Communicable Diseases Intelligence Vol 35 Number 2, June 2011 and may be downloaded as a full version PDF file (1854 KB).
Results, cont'd
Bloodborne diseases
In 2009, the bloodborne viruses reported to the NNDSS were hepatitis B, C, and D. Both hepatitis B and C cases are notified to the NNDSS as either ‘newly acquired’, where evidence was available that the infection was acquired within 24 months prior to diagnosis; or ‘greater than 2 years or unspecified’ period of infection. These categories were reported from all states and territories except Queensland where all cases of hepatitis C, including newly acquired, were reported as ‘greater than 2 years or unspecified’. The determination of a case as ‘newly acquired’ is heavily reliant on public health follow-up, with the method and intensity of follow-up varying by jurisdiction and over time.
In interpreting these data it is important to note that changes in notifications over time may not solely reflect changes in disease prevalence or incidence. Testing policies11 and screening programs, including the preferential testing of high risk populations such as persons in prison, injecting drug users and persons from countries with a high prevalence of hepatitis B or C, may contribute to these changes.
Information on exposure factors relating to the most likely source(s) or risk factors of infection for hepatitis B and C was reported in a subset of diagnoses of newly acquired infections. The collection of these enhanced data are also dependant on the level of public health follow-up, which is variable by jurisdiction and over time.
Further information regarding the surveillance of these infections are described within the hepatitis B and hepatitis C sections.
Notifications of HIV and AIDS diagnoses are reported directly to the Kirby Institute, which maintains the National HIV Registry and the National AIDS Registry. Information on national HIV/AIDS surveillance can be obtained from the Kirby Institute website 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 more 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 2009, there were 7,345 notifications of hepatitis B (both newly acquired and unspecified), equating to a rate of 33.6 notifications per 100,000 population. Following a peak in hepatitis B notifications between 2000 and 2001 (41.3 and 39.9 per 100,000 population, respectively), the overall hepatitis B notification rate declined and remained relatively stable at around 32 notifications per 100,000 population between 2003 and 2009 (Figure 4). Of the jurisdictions, the Northern Territory recorded the highest rate of hepatitis B notifications in 2009 (69.4 per 100,000 population), followed by New South Wales (37.8 per 100,000 population) and Victoria (37.5 per 100,000 population).
Since the introduction of the adolescent hepatitis B vaccination program for children aged 10–13 years in 1997 and the universal infant program in 2000,12 there has been a general decline in overall hepatitis B notification rates, especially amongst the 15–19 and 20–29 years age groups. In 2009, one notification of newly acquired hepatitis B and 5 notifications of hepatitis B (unspecified) were reported in children in the 0–4 years age group, representing 0.4% and 0.1% of hepatitis notifications in these categories, respectively. Approximately 93% of the 2008 Australian birth cohort received the full course of the hepatitis B vaccine.13–17
Newly acquired hepatitis B notifications
In 2009, 238 newly acquired hepatitis B notifications (1.1 per 100,000 population) were reported to the NNDSS, which was fewer than the number reported in 2008 (258 notifications; 1.2 per 100,000 population). The 2009 notification rate was the lowest since 1999, 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, 1999 to 2009, by year‡
* Data for newly acquired hepatitis B for the Northern Territory (1999–2004) includes some unspecified hepatitis B cases.
† Data for unspecified hepatitis B for all jurisdictions except the Northern Territory between 1999 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 2009 that were documented as newly acquired cases was 3.2%, compared with 3.8% in 2008. The proportion of newly acquired infections compared with total hepatitis B infections varied substantially: Tasmania (9%); the Australian Capital Territory, Queensland and Western Australia (5%); Victoria (4%); the Northern Territory (3%); South Australia (2%); and New South Wales (1%). The highest notification rates of newly acquired hepatitis B infection were reported from the Northern Territory (1.8 per 100,000 population), closely followed by Western Australia (1.7 per 100,000 population) and Victoria and Tasmania (1.6 per 100,000 population). The identification and classification of newly acquired hepatitis B is reliant upon public health follow-up, the extent of which varies between jurisdictions and over time.
In 2009, the highest notification rate of newly acquired hepatitis B infection was observed in the 25–29 years age group amongst males (3.9 per 100,000 population) and in the 35–39 years age group amongst females (2.5 per 100,000 population) (Figure 5). Overall, notifications of newly acquired hepatitis B infection were higher amongst males, with a male to female ratio of 1.9:1.
Figure 5: Notification rate for newly acquired hepatitis B, Australia, 2009, by age group and sex
Trends in newly acquired hepatitis B infection by year and age group are shown in Figure 6. Between 2000 and 2009, the notification rate of newly acquired hepatitis B fell substantially amongst persons aged 15–19 years (87%) and 20–29 years (71%). These trends occurred in both sexes.
Figure 6: Notification rate for newly acquired hepatitis B,* Australia, 1999 to 2009, by age group and year
* Data for newly acquired hepatitis B for the Northern Territory (1998–2004) includes some unspecified hepatitis B cases.
Of the 238 newly acquired hepatitis B notifications reported in 2009, the exposure history of 150 notifications from all jurisdictions except Queensland and Western Australia were assessed (Table 9). In 2009, 59% of these notifications had at least one risk factor recorded, with the source of exposure not recorded or unable to be determined for the remainder of these cases. Between 2006 and 2009, the proportion of notifications associated with injecting drug use declined from 43%18 to 33%. The proportion of diagnoses reporting a history of heterosexual contact with a hepatitis B positive partner also decreased from 21% in 2005 to 12% in 2009. Additional information was also collected on the country of birth of newly acquired cases from all jurisdictions except Queensland. The majority of these newly acquired diagnoses occurred amongst Australian-born persons, and the proportion of overseas-born people with hepatitis B was similar to the proportion of overseas-born people in the Australian population.18
Table 9: Newly acquired hepatitis B notifications, selected jurisdictions,* 2009, by sex and exposure category†
| Number of exposure factors reported† | ||||
|---|---|---|---|---|
Exposure category |
Male | Female | Total | Percentage‡ of notifications* (n = 150) |
| Injecting drug use | 32 |
18 |
50 |
33.3 |
| Imprisonment | 7 |
1 |
8 |
5.3 |
| Skin penetration procedure | 10 |
6 |
16 |
10.7 |
| Tattoos | 9 |
4 |
13 |
8.7 |
| Ear or body piercing | – |
2 |
2 |
1.3 |
| Acupuncture | 1 |
– |
1 |
0.7 |
| Healthcare exposure | 7 |
5 |
12 |
8.0 |
| Surgical Work | 4 |
2 |
6 |
4.0 |
| Major Dental Surgery | – |
2 |
2 |
1.3 |
| Blood/tissue recipient | 2 |
1 |
3 |
2.0 |
| Haemodialysis | 1 |
– |
1 |
0.7 |
| Sexual contact – hepatitis B positive partner | 14 |
9 |
23 |
15.3 |
| Opposite sex | 11 |
9 |
20 |
13.3 |
| Same sex | 3 |
– |
3 |
2.0 |
| Household contact | 5 |
6 |
11 |
7.3 |
| Needlestick or bio-hazardous injury§ | 1 |
– |
1 |
0.7 |
| Other | 22 |
8 |
30 |
20.0 |
| Sexual contact – unknown hepatitis B status partner|| | 16 |
4 |
20 |
13.3 |
| Notifications with at least one risk factor recorded | 60 |
28 |
88 |
58.7 |
| Risk factor unable to be determined | 3 |
2 |
5 |
3.3 |
| Unknown (not recorded) | 36 |
21 |
57 |
38.0 |
| Total number of exposure factors reported† | 137 |
76 |
213 |
– |
| Total number of notifications* | 99 |
51 |
150 |
– |
* Notifications from the Australian Capital Territory, New South Wales, the Northern Territory, South Australia, Tasmania and Victoria.
† More than one exposure category for each notification could be recorded.
‡ The denominator used to calculate the percentage is based on the total number of notifications from all jurisdictions, except Queensland and Western Australia. As more than one exposure category for each notification could be recorded, the total percentage does equate to 100%.
§ Includes both occupational and non-occupational exposures.
|| Established through analysis of free text field.
Unspecified hepatitis B notifications
In 2009, a total of 7,107 notifications of unspecified hepatitis B infection were reported to the NNDSS, compared with 6,518 notifications in 2008. The Northern Territory recorded the highest notification rate (67.6 per 100,000 population), followed by New South Wales (37.3 per 100,000 population) and Victoria (35.9 per 100,000 population).
The notification rate of hepatitis B (unspecified) has declined by 23% since 2001 (39.5 per 100,000 population) with the lowest annual rate observed in 2004 (28.5 per 100,000 population) (Figure 4). Since 2001, there has been a slight upward trend in the notification rate for hepatitis B (unspecified), with a rate of 32.5 per 100,000 population observed in 2009.
In 2009, sex was recorded in 7,019 of the 7,107 notifications (99%). The male to female ratio of notifications was 1.2:1. Notification rates were highest in males aged 25 to 44 years, peaking in the 30–34 years age group (74.1 notifications per 100,000 population). Among females, notification rates were highest in the 25–29 years age group (77.2 per 100,000 population), followed by the 30–34 years age group (71.5 per 100,000 population) (Figure 7).
Figure 7: Notification rate for unspecified hepatitis B, Australia, 2009, by age group and sex*
* Excluding 94 cases whose sex or age were not reported.
Trends in hepatitis B (unspecified) infection by year and age group are shown in Figure 8. Rates across most age groups were slightly higher in 2009 compared with 2008, with the 30–39 years age group increasing by 9.2% (58.7 to 64.1 notifications per 100,000 population). The highest notification rates continued to be observed amongst the 20–29 and 30–39 years age groups (59.7 and 64.1 per 100,000 population, respectively).
Figure 8: Notification rate for unspecified hepatitis B,* Australia, 1999 to 2009, by age group and year
* Data for hepatitis B (unspecified) from all states except the Northern Territory between 1999 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 more 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 negative test result within 24 months prior to laboratory diagnosis or clinical hepatitis within the 24 months prior to a positive diagnostic test where other causes of acute hepatitis have been excluded. Ascertainment of a person’s hepatitis C testing and clinical history usually requires active follow-up by public health units.
Between 1999 and 2009, total hepatitis C notification rates declined by 49.5% (104 to 52.5 notifications per 100,000 population), with the greatest reductions observed between 1999 and 2002 (24% decline) (Figure 9). These reductions followed a peak in case notifications associated with the detection and accounting of prevalent cases that occurred in the late 1990s through the expansion of testing in high risk groups.19 The continuing decline in the notification rate may be attributable to reductions in risk behaviours related to injecting drug use, especially amongst young people, and the implementation of needle exchange programs.19,20
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.21 In 2009, it was estimated that 291,000 people living in Australia had been exposed to the hepatitis C virus. Of these, approximately 165,000 had chronic hepatitis C infection and early liver disease, 46,000 had chronic hepatitis C infection with moderate liver disease, 5,900 were living with hepatitis C related cirrhosis and 74,000 had cleared their infection.18
Newly acquired hepatitis C notifications
Notifications of newly acquired hepatitis C were reported from all jurisdictions except Queensland, where all cases of hepatitis C, regardless of whether they are newly acquired, are reported as unspecified. There were 401 newly acquired hepatitis C notifications reported in 2009 (362 notifications in 2008), giving a notification rate of 2.3 per 100,000 population (Figure 9).
Figure 9: Notification rate for newly acquired hepatitis C* and unspecified hepatitis C,† Australia, 1999 to 2009, by year
* Data for newly acquired hepatitis C from all states and territories except Queensland 1999 to 2009 and the Northern Territory 1999 to 2002.
† Data for unspecified hepatitis C provided from Queensland (1999–2009) and the Northern Territory (1999–2002) includes both newly acquired and unspecified hepatitis C cases.
Of all hepatitis C notifications in 2009, 3.5% were identified as newly acquired infections, which is comparable to previous years. Amongst jurisdictions, the proportion of newly acquired infections compared with total hepatitis C diagnoses varied substantially, with 8% in South Australia, Western Australia and Victoria; 7% in Tasmania; 4% in the Australian Capital Territory; 3% in the Northern Territory, and 1% in New South Wales. The highest rates of newly acquired hepatitis C infection were reported in Tasmania and Western Australia (4.2 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 method and extent of case follow-up, and the population groups targeted, vary among jurisdictions, with newly acquired infection more likely to be detected in population groups that are tested frequently, such as those in prison settings.
Notification rates of newly acquired hepatitis C were highest in males in the 20–24 years age group followed by the 25–29 and 30–34 years age groups (11.2, 8.4 and 7.5 per 100,000 population, respectively). Peaks in the female population occurred in the 20–24 and 25–29 years age groups at around 6.5 notifications per 100,000 population (Figure 10).
Figure 10: Notification rate for newly acquired hepatitis C, Australia,* 2009, by age group and sex
* Data from all states and territories except Queensland.
Trends in the age distribution of newly acquired hepatitis C infection are shown in Figure 11. While rates for individual age groups vary from year to year, declines continue to be observed in the 15–19 and 20–29 years age groups. Annual rates in the other age groups continued to be relatively stable over the 1999 to 2009 period.
Figure 11: Notification rate for newly acquired hepatitis C, Australia,* 1999 to 2009, by age group and year
* Data from all states and territories except Queensland (1999–2009) and the Northern Territory (1999–2002).
Exposure history surveillance data for all newly acquired hepatitis C notifications reported in 2009 were assessed from all jurisdictions except Queensland (Table 10). In 2009, 80% of these notifications had at least one risk factor recorded, with the source of exposure not recorded or unable to be determined for the remainder of these cases. Approximately 67% of notifications had a history of injecting drug use (42% of which with injecting drug use in the 24 months prior to diagnosis), and 19% had been detained in a correctional facility within the 24 months prior to diagnosis. Screening rates are generally higher in the prison entry population than the general population. A screening survey of prison entrants conducted over a two-week period in 2007 found that the prevalence of hepatitis C, based on hepatitis C antibody detection, was 35%.13
Table 10: Newly acquired hepatitis C notifications, selected jurisdictions,* 2009, by sex and exposure category†
| Number of exposure factors reported† | ||||
|---|---|---|---|---|
Exposure category |
Male | Female | Total | Percentage‡ of notifications* (n = 401) |
| Injecting drug use | 166 |
101 |
267 |
66.6 |
| Imprisonment | 68 |
8 |
76 |
19.0 |
| Skin penetration procedure | 48 |
24 |
72 |
18.0 |
| Tattoos | 34 |
13 |
47 |
11.7 |
| Ear or body piercing | 13 |
10 |
23 |
5.7 |
| Acupuncture | 1 |
1 |
2 |
0.5 |
| Healthcare exposure | 4 |
12 |
16 |
4.0 |
| Surgical Work | 3 |
11 |
14 |
3.5 |
| Major Dental Surgery | 1 |
1 |
2 |
0.5 |
| Blood/tissue recipient | – |
– |
– |
0.0 |
| Sexual contact – hepatitis C positive partner | 14 |
25 |
39 |
9.7 |
| Opposite sex | 12 |
24 |
36 |
9.0 |
| Same sex | 2 |
1 |
3 |
0.7 |
| Household contact | 6 |
12 |
18 |
4.5 |
| Perinatal transmission | 11 |
12 |
23 |
5.7 |
| Needlestick or bio-hazardous injury§ | 3 |
2 |
5 |
1.2 |
| Other | 6 |
9 |
15 |
3.7 |
| Notifications with at least one risk factor | 193 |
127 |
320 |
79.8 |
| Risk factor unable to be determined | 11 |
6 |
17 |
4.2 |
| Unknown (not recorded) | 41 |
23 |
64 |
16.0 |
| Total number of exposure factors reported† | 378 |
234 |
612 |
– |
| Total number of notifications* | 245 |
156 |
401 |
– |
* Includes diagnoses in the Australian Capital Territory, New South Wales, South Australia, Tasmania, Victoria, Western Australia and the Northern Territory.
† More than one exposure category for each notification could be recorded.
‡ The denominator used to calculate the percentage is based on the total number of notifications from all jurisdictions, except Queensland. As more than one exposure category for each case could be recorded, the total percentage does not equate to 100%.
§ Includes both occupational and non-occupational exposures.
Unspecified hepatitis C notifications
In 2009, 11,081 unspecified hepatitis C infections were notified to the NNDSS (50.7 per 100,000 population) compared with 11,098 notifications in 2008 (51.8 per 100,000 population).
The national notification rate for unspecified hepatitis C infection declined from 101.6 per 100,000 population in 1999 to 50.7 per 100,000 population in 2009 (Figure 9). Several factors may account for the decrease: changes in surveillance practices, including duplicate notification checking; a gradual decline in the prevalent group of hepatitis C cases accumulated prior to the introduction of hepatitis C testing in the early 1990s; and general reductions in risk behaviours related to injecting drug use, including the implementation of needle exchange programs.18–20
In 2009, the Northern Territory continued to have the highest notification rate (71.2 per 100,000 population) followed by New South Wales (55.1 per 100,000 population) and Tasmania (52.1 per 100,000 population). Queensland’s rate was also high, at 61.5 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. Amongst males, notification rates were highest across the age group range 30–34 to 50–54 years at around 129 per 100,000 population (range: 127.8 to 136.3). In the female population, notification rates were highest in the 25–29 and 30–34 years age groups, at 78.7 and 74.3 per 100,000 population respectively (Figure 12).
Figure 12: Notification rate for unspecified hepatitis C,* Australia, 2009, by age group and sex†
* Data provided from Queensland includes both newly acquired and unspecified hepatitis C cases.
† Excludes 60 cases whose age or sex was not reported.
Trends in the age distribution of unspecified hepatitis C infection are shown in Figure 13. Between 2000 and 2009, the notification rate of unspecified hepatitis C declined by 82% amongst the 15–19 years age group, by 66% amongst the 20–29 years age group and by 49% in the 30–39 years 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, 1999 to 2009, by age group and year
* Data provided from Queensland (1999–2009) and the Northern Territory (1999–2002) includes both newly acquired and unspecified hepatitis C cases.
Hepatitis D
Hepatitis D is a defective single-stranded ribonucleic acid virus (RNA) that replicates in the presence of the hepatitis B virus. Hepatitis D infection can occur either as a co-infection with hepatitis B or as a super-infection with chronic hepatitis B infection.21 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 2009, there were 34 notifications of hepatitis D (0.2 per 100,000 population) reported from Queensland (13), Victoria (12) and New South Wales (9). Over the past 5 years, notifications of hepatitis D have continued to remain relatively stable at around 34 notifications per year (range: 29 to 42), and over this time the male to female ratio was around 3:1 (Figure 14).
Figure 14: Notifications of hepatitis D, Australia, 1999 to 2009, by sex
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This issue - Vol 35 No 2, June 2011
NNDSS Annual report 2009