This extract of the NNDSS annual report 2010 was published in Communicable Diseases Intelligence Vol 36 No 1 March 2012. A print friendly full version may be downloaded as a PDF 1862 KB.
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Results, cont'd
Bloodborne diseases
In 2010, 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 notified cases over time may not solely reflect changes in disease prevalence or incidence. Testing policies such as the National Hepatitis C Testing Policy10 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 is described within the hepatitis B and hepatitis C sections.
Hepatitis B
Hepatitis B notifications are classified as either ‘newly acquired’ or ‘unspecified’ as described above. 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 2010, there were 7,106 diagnoses of hepatitis B (both newly acquired and unspecified) reported, equating to a rate of 31.9 cases per 100,000 population (Figure 4). The Northern Territory recorded the highest hepatitis B diagnosis rate in 2010 (69.7), followed by Victoria (35.3) and Western Australia (35.2).
Since the introduction of the adolescent hepatitis B vaccination program for children aged between 10 and 13 years in 1997 and the universal infant program in 2000,11 there has been a general decline in overall rates of hepatitis B. Between 2000 and 2010 unspecified hepatitis B rates decreased 22% from 39.5 to 30.8 and newly acquired hepatitis B rates decreased from a rate of 2.2 to 1.0 (Figure 4). Approximately 92% of the 2010 Australian birth cohort received the full primary course of the hepatitis B vaccine by 15 months of age.12
Newly acquired hepatitis B
In 2010, there were 228 notified cases of newly acquired hepatitis B (1.0 per 100,000 population) reported to the NNDSS; a 4% decrease compared with the 238 cases (rate of 1.1) reported in 2009 and a continuation of the downward trend in notified cases (Figure 4).
Figure 4: Rate for newly acquired hepatitis B* and unspecified hepatitis B,† Australia, 2000 to 2010, by year‡
* Data for newly acquired hepatitis B for the Northern Territory (2000–2004) includes some unspecified hepatitis B cases.
† Data for unspecified hepatitis B for all jurisdictions except the Northern Territory between 2000 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 cases in 2010 that were documented as newly acquired continued to trend downward and was 3.2%, compared with 3.3% in 2009 and 5.2% in 2000. The proportion of newly acquired infections compared to total hepatitis B infections varied substantially: Tasmania (11%); Queensland (5.2%), South Australia (4.9%); Western Australia (4.1%); Victoria (3.5%); the Australian Capital Territory (3.1%); the Northern Territory (1.9%) and New South Wales (1.4%). The highest rates were reported from Western Australia (1.4), closely followed by the Northern Territory, Queensland and South Australia (all 1.3) and Tasmania and Victoria (1.2).
Overall, cases were more common amongst males, with a male to female ratio of 1.9:1. In 2010, the highest rate of newly acquired hepatitis B infection was observed amongst males 35–39 and 40–44 years (3.0 and 3.1 respectively) (Figure 5).
Figure 5: Rate for newly acquired hepatitis B,* Australia, 2010, 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 2010, most age group rates have been trending down with the most marked decreases occurring among the 15–19 year and 20–29 year age groups. There were 5 cases, all female, in the 0–4 year age group in 2010, the highest number since 4 cases were reported in 2006 and well above the average of 1.6 for the previous 5 years.
Figure 6: Rate for newly acquired hepatitis B,* Australia, 2000 to 2010, by year and age group
* Data for newly acquired hepatitis B for the Northern Territory (1998–2004) includes some unspecified hepatitis B cases.
Of the 228 cases reported in 2010, the exposure history of 120 cases from New South Wales, Victoria, South Australia and the Northern Territory were assessed (Table 9). In 2010, 73% (n = 87) of these cases had at least one risk factor recorded, with the source of exposure not recorded or unable to be determined for the remainder. Injecting drug use remains the most frequently reported source of infection in 2010 but has declined as a proportion of reported cases from 52% in 2006 to 39% in 2010. Skin penetration procedures were the next most frequently reported source of infection (15%), the majority of which were reported as tattoos.
Table 9: Notified cases of newly acquired hepatitis B cases,* selected jurisdictions, 2010, by sex and exposure category†
Exposure category |
Number of exposure factors reported† | Percentage of cases* (n = 120) | ||
|---|---|---|---|---|
| Male | Female | Total | ||
| Injecting drug use | 29 |
18 |
47 |
39.2 |
| Imprisonment | 9 |
1 |
10 |
8.3 |
| Skin penetration procedure | 10 |
8 |
18 |
15.0 |
| Tattoos | 8 |
4 |
12 |
10.0 |
| Ear or body piercing | 2 |
3 |
5 |
4.2 |
| Acupuncture | 0 |
1 |
1 |
0.8 |
| Healthcare exposure | 9 |
2 |
11 |
9.2 |
| Surgical work | 6 |
1 |
7 |
5.8 |
| Major dental surgery work | 1 |
1 |
2 |
1.7 |
| Blood/tissue recipient | 0 |
0 |
0 |
0.0 |
| Haemodialysis | 2 |
0 |
2 |
1.7 |
| Sexual contact – hepatitis B positive partner | 5 |
7 |
12 |
10.0 |
| Opposite sex | 4 |
6 |
10 |
8.3 |
| Same sex | 1 |
1 |
2 |
1.7 |
| Household contact | 4 |
5 |
9 |
7.5 |
| Needlestick/biohazardous injury§ | 2 |
0 |
2 |
1.7 |
| Perinatal transmission | 1 |
1 |
2 |
1.7 |
| Other | 10 |
7 |
17 |
14.2 |
| Sexual contact – unknown HBV status|| | 6 |
4 |
10 |
8.3 |
| Cases with at least one risk factor | 56 |
31 |
87 |
72.5 |
| Undetermined | 11 |
6 |
17 |
14.2 |
| Unknown (not recorded) | 10 |
6 |
16 |
13.3 |
| Total exposure factors reported† | 100 |
61 |
161 |
– |
| Total number of cases* | 77 |
43 |
120 |
– |
* Cases from New South Wales, the Northern Territory, South Australia, and Victoria.
† More than one exposure category for each case could be recorded. ‡ The denominator used to calculate the percentage is based on the total number of cases from all jurisdictions (New South Wales, the Northern Territory, South Australia, and Victoria). As more than one exposure category for each notification could be recorded, the total percentage does not equate to 100%. § Includes both occupational and non-occupational exposures.
|| Established through analysis of free text field.
Additional information was also collected on the country of birth (COB) from all jurisdictions except Queensland. Of the 137 cases in which COB was reported, the majority occurred amongst Australian born persons (66%, n = 90) with the remaining 47 cases amongst those born overseas. The proportion of overseas-born people with hepatitis B was similar to the proportion of overseas born people in the Australian population for Europe and the Americas and higher for those born in North Africa and the Middle East and Asia.13
Unspecified hepatitis B notifications
In 2010, there were 6,878 notified cases of unspecified hepatitis B infection reported to the NNDSS, a rate of 31 per 100,000 population, compared with 7,094 cases (and a rate of 32) in 2009.
The overall rate of hepatitis B (unspecified) has been trending downward over the past 11 years with the majority of this decrease occurring between 2000 and 2004. Between 2005 and 2010 the rate has remained relatively stable with an average annual rate of 31 during this time (Figure 4).
In 2010, the overall male rate (33) was higher than for females (28), a rate ratio of 1.2:1, but females had the highest age specific rate amongst those in the 25–29 year age group (78) compared with the highest age specific rate amongst males of 71 in the 30–34 year age group (Figure 7).
Figure 7: Rate for unspecified hepatitis B, Australia, 2010, by age group and sex
Trends in hepatitis B (unspecified) infection by year and age group are shown in Figure 8. Rates across all age groups have declined since 2000 with the majority of this decrease occurring in the first 3 years, before stabilising. The biggest decrease (47%) has occurred amongst the 15–19 year age group declining from a rate of 36 in 2000 to 19 in 2010.
Figure 8: Rate for unspecified hepatitis B,* Australia, 2000 to 2010, by year and age group
* Data for hepatitis B (unspecified) from all states and territories except the Northern Territory between 2000 and 2004.
The Northern Territory recorded the highest rate (68), followed by Victoria, New South Wales and Western Australia (all 34).
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 2000 and 2010, total hepatitis C notification rates declined by 50% (101 to 50 per 100,000), with the greatest reductions observed in the earlier years, (a 16% decline between 2001 and 2002) (Figure 9). These reductions followed a peak in notified cases associated with the detection and notification of prevalent cases that occurred in the late 1990s through the expansion of testing in high risk groups.14 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.14,15
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 these, half will eventually develop cirrhosis or cancer of the liver.16 In 2010, it was estimated that 297,000 people living in Australia had been infected with the hepatitis C virus. Of these, approximately 168,000 had chronic hepatitis C infection and early liver disease, 48,000 had chronic hepatitis C infection with moderate liver disease, 6,100 were living with hepatitis C related cirrhosis and 76,000 had cleared their infection.13
Newly acquired hepatitis C notifications
Cases of newly acquired hepatitis C were reported from all states and territories except Queensland, where all cases of hepatitis C are reported as unspecified. There were 358 notified cases reported in 2010 compared with 401 notified cases in 2009, giving a rate of 2.0 per 100,000 population (Figure 9).
Figure 9: Rates for newly acquired hepatitis C* and unspecified hepatitis C,† Australia, 2000 to 2010, by year
* Data for newly acquired hepatitis C from all states and territories except Queensland 2000–2010 and the Northern Territory 2000–2002.
† Data for unspecified hepatitis C provided from Queensland (2000–2010) and the Northern Territory (2000–2002) includes both newly acquired and unspecified hepatitis C cases.
Of all hepatitis C cases in 2010, 3% were identified as newly acquired infections, which is comparable to previous years. The proportion of newly acquired infections compared with total hepatitis C diagnoses varied substantially amongst the states and territories with 9% in South Australia; 8% in Tasmania; 7% in Western Australia; 6% in Victoria; 5% in the Australian Capital Territory; and 1% in New South Wales. No newly acquired cases were recorded for the Northern Territory or Queensland. The highest rates of newly acquired hepatitis C infection were reported in Tasmania (4.3 per 100,000), followed by Western Australia (3.5) and the Australian Capital Territory (3.3 per 100,000). 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 amongst states and territories, with newly acquired infection more likely to be detected in population groups that are tested frequently, such as those in prison settings.
The male to female ratio was 1.6:1 with the highest rate amongst males in the 20–24 year age group followed by the 25–29 year age group and the 30–34 year age group (8.4, 7.0 and 5.2 respectively). The highest age group rates for females were consistent with males, occurring in the 20–24 year age group followed by the 25–29 and 30–34 year age groups (5.6, 4.7 and 3.4 respectively) (Figure 10).
Figure 10: Rate for newly acquired hepatitis C, Australia* 2010, 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 year age groups. Annual rates in the other age groups continued to be relatively stable over the 2000 to 2010 period.
Figure 11: Rate for newly acquired hepatitis C, Australia,* 2000 to 2010, by year and age group
* Data from all states and territories except Queensland (2000–2010) and the Northern Territory (2000–2002).
Exposure history surveillance data for 91% of newly acquired hepatitis C cases reported in 2010 were assessed from all jurisdictions except Queensland (Table 10). In 2010, 75% of these cases 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. Seventy-nine per cent of notifications had a history of injecting drug use (57% of which reported injecting drug use in the 24 months prior to diagnosis). Skin penetration procedures and imprisonment accounted for 26% and 22% of reported risk factors respectively, noting that screening rates are generally 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%.17
Table 10: Notified cases of newly acquired hepatitis C, selected jurisdictions,* 2010, by sex and exposure category†
Exposure category |
Number of exposure factors reported† | Percentage‡ of cases* (n = 325) | ||
|---|---|---|---|---|
| Male | Female | Total | ||
| Injecting drug use | 156 |
102 |
258 |
79.4 |
| Imprisonment | 64 |
7 |
71 |
21.8 |
| Skin penetration procedure | 56 |
28 |
84 |
25.8 |
| Tattoos | 34 |
15 |
49 |
15.1 |
| Ear or body piercing | 21 |
12 |
33 |
10.2 |
| Acupuncture | 1 |
1 |
2 |
0.6 |
| Healthcare exposure | 12 |
13 |
25 |
7.7 |
| Surgical Work | 5 |
10 |
15 |
4.6 |
| Major dental surgery work | 4 |
2 |
6 |
1.8 |
| Blood/tissue recipient | 3 |
0 |
3 |
0.9 |
| Haemodialysis | 0 |
1 |
1 |
0.3 |
| Sexual contact – hepatitis B positive partner | 27 |
15 |
42 |
12.9 |
| Opposite sex | 22 |
14 |
36 |
11.1 |
| Same sex | 5 |
1 |
6 |
1.8 |
| Household contact | 12 |
8 |
20 |
6.2 |
| Perinatal transmission | 22 |
7 |
29 |
8.9 |
| Needlestick/biohazardous injury§ | 3 |
0 |
3 |
0.9 |
| Other | 8 |
9 |
17 |
5.2 |
| Notifications with at least one risk factor | 138 |
107 |
245 |
75.4 |
| Undetermined | 46 |
14 |
60 |
18.5 |
| Unknown or missing (not recorded) | 11 |
9 |
20 |
6.2 |
| Total exposure factors reported† | 417 |
212 |
629 |
– |
| Total cases* | 195 |
130 |
325 |
– |
* Includes diagnoses in all states and territories except Queensland.
† 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 2010, there were 10,803 notified cases of unspecified hepatitis C infections (48 per 100,000 population) compared with 11,081 notified cases in 2009 and a rate of 51 per 100,000 population. This continues the downward trend and represents a 51% decline compared with 2000, when the rate was 98 per 100,000 population.
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.14,15,18
The male to female ratio remained consistent with historical trends at 1.7:1 in 2010. Amongst males, rates were highest across age groups between 30 and 54 years ranging from 111 to 122. Females rates were similarly highest amongst adults in the 30–34 year age group (80 per 100,000) followed by the 25–29 year (67 per 100,000) and 35–39 year age groups (66 per 100,000) (Figure 12).
Figure 12: Rate for unspecified hepatitis C,* Australia, 2010 by age group and sex
* Data provided from Queensland includes both newly acquired and unspecified hepatitis C cases.
The rate of unspecified hepatitis C declined in all age groups with the biggest decreases occurring amongst the 15–19 year age group (82%), the 20–29 year (68%) and the 30–39 year age groups (51%). The majority of this decline occurred in the early part of the decade. Trends in the 0–4, 5–14 and the 40 years or over age groups have remained relatively stable over this time (Figure 13).
Figure 13: Rate for unspecified hepatitis C,* Australia, 2000 to 2010, by year and age group
* Data provided from Queensland (2000–2010) and the Northern Territory (2000–2002) includes both newly acquired and unspecified hepatitis C cases.
In 2010, the Northern Territory continued to have the highest rate (75 per 100,000) followed by Queensland (61 per 100,000) and the Australian Capital Territory (59 per 100,000), noting that Queensland’s rate includes both newly acquired and unspecified cases. The lowest rate was in South Australia (30 per 100,000) (Table 5).
Hepatitis D
Hepatitis D is a defective single-stranded RNA virus 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.16 The modes of hepatitis D transmission are similar to those for hepatitis B, and in countries with low hepatitis B prevalence such as Australia, injecting drug users are therefore likely to be the main group at risk for hepatitis D.
In Australia, the rate of hepatitis D remains low. In 2010, there were 35 notified cases of hepatitis D, a rate of 0.2 per 100,000 population, reported from Queensland (n = 20), New South Wales (n = 9) and Victoria (n = 6). Reported cases of hepatitis D have had a slight increasing trend with case numbers in 2010 above the average of 30 cases notified per year (range: 20–42) between 2000 and 2009. The male female ratio in 2010 was 3.4:1 consistent with the average ratio of 3:1 in the preceding 5 years (Figure 14).
Figure 14: Notified cases of hepatitis D, Australia, 2000 to 2010, by year and sex
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This issue - Vol 36 No 1, March 2012
NNDSS Annual report 2010