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. Information on national HIV and AIDS surveillance can be obtained from the NCHECR website at http://www.nchecr.unsw.edu.au4
Hepatitis B
Hepatitis B notifications are classified as either newly acquired (incident) hepatitis B or hepatitis B with an unspecified period of infection. Classification of hepatitis B cases as newly acquired is based on serological evidence or evidence of a previously negative test within the last 24 months.
Incident hepatitis B notifications
In 2007, 287 cases of incident hepatitis B infection were reported to NNDSS, which was lower than in 2006 (n=294). Over the past 10 years, the notification rate for incident hepatitis B infection increased from 1.5 cases per 100,000 population in 1997 to 2.2 cases per 100,000 population in 2001, then declined to 1.2 cases per 100,000 population in 2005 and increased to 1.4 cases per 100,000 population in 2006 and 2007 (Figure 4).
Figure 4: Notification rate for incident hepatitis B* and hepatitis B (unspecified),† Australia, 1997 to 2007, by year‡
* Data for incident hepatitis B from all states except the Northern Territory between 1997 and 2004.
† Data provided from the Northern Territory (1997–2004) includes both incident and unspecified hepatitis B cases.
‡ Year of onset for incident hepatitis B and year of notification for hepatitis B (unspecified) notifications.
The Northern Territory and the Australian Capital Territory recorded the highest notification rates in 2007 with 4.2 and 3.8 cases per 100,000 population respectively. At a regional level, incident hepatitis B rates were highest in the Barkly, Lower Top End and East Arnhem Statistical Subdivisions of the Northern Territory (range: 5.4–15.9 cases per 100,000 population, 5 cases total); and in the Far North and South West Statistical Divisions of Queensland, the Upper Great Southern Statistical Division in Western Australia, and in the East Gippsland, Central Highlands and Barwon Statistical Divisions of Victoria (range: 3.2–5.3 cases per 100,000 population) (Map 2).
Map 2: Notification rates for incident hepatitis B, Australia, 2007, by Statistical Division of residence and Statistical Subdivision for the Northern Territory
In 2007, the sex of cases was reported in 286 of the 287 cases. Figure 5 shows that the highest rate of incident hepatitis B infection was in the 25–29 years age group among both males and females (4.4 and 3.4 cases per 100,000 population, respectively). Notifications of incident hepatitis B infection in males exceeded those in females, with a male to female ratio of 1.8:1.
Figure 5: Notification rate for incident hepatitis B infections, Australia, 2007, by age group and sex*
* Excludes one case whose sex was not reported.
Trends in incident hepatitis B infection by year and age group are shown in Figure 6. Since the introduction of the adolescent hepatitis B vaccination program for children aged 10–13 years in 199713 there has been a general decline in hepatitis B among the 15–19 years and 20–29 years age groups. Between 2000 and 2007, the notification rate for incident hepatitis B fell by 75% among cases in the 15–19 years age group. In the 20–29 years age group, the notification rate fell by 55% between 2000 and 2005 and has remained stable at around 3.2 cases per 100,000 population from 2005 to 2007.
Figure 6: Notification rate for incident hepatitis B infections, Australia, 1997 to 2007, by year and age group
* Data provided from the Northern Territory (1997–2004) includes both incident and unspecified hepatitis B cases.
The source of exposure for cases of incident hepatitis B infection in 2007 was reported through health authorities in South Australia, Tasmania and Victoria (Table 9). From 2003 to 2007, the proportion of notifications of incident hepatitis B infection associated with injecting drug use remained relatively stable at around 49%. The proportion of diagnoses attributed to heterosexual contact decreased from 21% in 2003 to 16% in 2007. The source of exposure to hepatitis B was undetermined in around 21% of cases.4
Table 9: Incident hepatitis B infection,* 2007, by exposure category†
Exposure category |
Number | Percentage (%) |
|---|---|---|
| Injecting drug use | 49 |
47.6 |
| Sexual contact | 20 |
19.4 |
| Male homosexual contact | 3 |
2.9 |
| Heterosexual contact | 17 |
16.5 |
| Not specified | 0 |
0 |
| Blood/tissue recipient | 0 |
0 |
| Skin penetration procedure | 4 |
3.9 |
| Healthcare exposure | 1 |
0.9 |
| Household contact | 5 |
4.9 |
| Other | 20 |
19.4 |
| Undetermined | 4 |
3.9 |
| Total exposures | 103 |
100 |
* Includes diagnoses in South Australia, Tasmania and Victoria.
† More than 1 exposure category for each case could be recorded.
Source: National Centre in HIV Epidemiology and Clinical Research.4
Hepatitis B (unspecified) notifications
In 2007, a total of 6,917 cases of hepatitis B (unspecified) infection were notified to the NNDSS, compared with 6,276 in 2006. The Northern Territory recorded the highest notification rate (112.1 cases per 100,000 population), followed by New South Wales (37.8 cases per 100,000 population) and Victoria (35.8 cases per 100,000 population).
In 2007, the sex of cases was recorded in 6,848 of 6,917 cases (99%). Of these cases, the male to female ratio of notifications was 1.2:1. Among males, the highest notification rate was in the 30–34 years age group (71.4 cases per 100,000 population), followed by the 25–29 and 35–39 years age groups at 65.6 cases per 100,000 population in both age groups. Among females, the highest notification rate was in the 25–29 years age group (83.3 cases per 100,000 population), followed by 66.7 cases per 100,000 population in the 30–34 years age group (Figure 7).
Figure 7: Notification rate for hepatitis B (unspecified) infection, Australia, 2007, by age group and sex*
* Excludes 69 cases whose sex was not reported.
Notification rates for hepatitis B infection (unspecified) increased from 37.8 cases per 100,000 population in 1997 to 41.3 in 2001 and then declined to around 30.3 cases per 100,000 population in 2006 (Figure 4). In 2007, the rate of hepatitis B (unspecified) notifications (32.9 cases per 100,000 population) remained consistent with the range of rates seen between 2003 and 2006 (29.2–31.0 cases per 100,000 population). Trends in hepatitis B (unspecified) infection by age group, sex and year are shown in Figure 8. Rates in the 15–19 years age group increased in 2007 by 12.1% compared with 2006 (22.3 and 19.9 cases per 100,000 population respectively), however, the 2007 rate in this age group is consistent with rates between 2003 and 2005 (range 20.9–25.2 cases per 100,000 population).
Figure 8: Notification rate for hepatitis B (unspecified) infection, Australia,* 1997 to 2007, by year and age group
* Data for hepatitis B (unspecified) from all states except the Northern Territory between 1997 and 2004.
In 2007, 1 case of incident hepatitis B and 17 cases of hepatitis B (unspecified) infection were notified in children in the 0–4 years age group and represented 0.4% and 0.3% of hepatitis cases notified in these specific categories respectively. Approximately 95% of infants born in Australia in 2007 received the full-course of the hepatitis B vaccine.4
Hepatitis C
Hepatitis C notifications are classified as either newly acquired (incident) hepatitis C or hepatitis C with a period of infection greater than 2 years or unspecified. The categorising of hepatitis C cases is complex as current testing methods cannot distinguish between incident and chronic infections (greater than 2 years or unspecified). Cases are essentially categorised based on evidence of a previously negative test result within 2 years of their diagnosis. In most instances this requires active follow-up by public health units.
Since 2001, there has been a steady decline in cases of hepatitis C nationally (Figure 9). Map 3 shows the distribution of both incident hepatitis C and hepatitis C of greater than 2 years or unspecified duration diagnosed during 2007. The highest rates of hepatitis C were seen in the Darwin and Darwin City Statistical Subdivisions (125.2 and 157.8 cases per 100,000 population respectively). Notification rates were also substantially above the national notification rate in the Kimberley Statistical Division of Western Australia; the Central and Barkly Statistical Subdivisions of the Northern Territory; the Far North Statistical Division of Queensland; and the Mid-North Coast, North Western and Central West Statistical Divisions of New South Wales (79.0–115.0 cases per 100,000 population).
Figure 9: Notification rates for incident hepatitis C infection* and hepatitis C (unspecified),† Australia, 1997 to 2007
* Data from all states and territories except Queensland 1997–2007 and the Northern Territory 1997–2002.
† Data provided from Queensland (1997–2007) and the Northern Territory (1997–2002) includes both incident and unspecified hepatitis C cases.
Map 3: Notification rates for incident hepatitis C and hepatitis C (unspecified), Australia, 2007, by Statistical Division of residence and Statistical Subdivision for the Northern Territory
Incident hepatitis C notifications
Notifications of incident hepatitis C were received from all jurisdictions except Queensland, where all cases of hepatitis C are reported as hepatitis C (unspecified). A total of 355 cases of incident hepatitis C were notified in 2007 (450 cases in 2006), giving a notification rate of 2.1 cases per 100,000 population (Figure 9).
The proportion of all hepatitis C notifications in 2007, excluding Queensland, that were documented as incident cases was 3.6%, compared with 4.5% in 2006. The highest rates of incident hepatitis C infection were reported from Tasmania (4.1 cases per 100,000 population) and Western Australia (3.6 cases per 100,000 population). The number of incident hepatitis C notifications in 2007, both nationally and for each jurisdiction, is influenced by the level of case follow-up. One possible explanation for the highest rate observed in Tasmania is the opportunity to detect additional cases through follow-up and repeated surveys.
In 2007, the sex of cases was reported in 354 of the 355 cases notified. Figure 10 shows that in 2007 the highest incident hepatitis C notification rates were in the 25–29 years age group in males (9.7 cases per 100,000 population). In females, notification rates were highest in the 15–19 years age group (4.8 cases per 100,000 population) followed by the 10–14 and 20–24 years age groups (4.6 and 4.4 cases per 100,000 population respectively).
Figure 10: Notification rate for incident hepatitis C infection, Australia,* 2007, by age group and sex†
* Data from all states and territories except Queensland.
† Excludes 1 case whose sex was not reported.
Trends in the age distribution of incident hepatitis C infection are shown in Figure 11. Notification rates from 2001 to 2007 declined by 62% in the 15–19 years age group; 59% in the 20–29 years age group; and by 44% in the 30–39 years age group. In 2006 to 2007, notification rates decreased by 26% in the 20–29 years age group and by 23% in the 30–39 years age group.
Figure 11: Notification rate for incident hepatitis C infection, Australia,* 1997 to 2007, by age group and year
* Data from all states and territories except Queensland (1997–2007) and the Northern Territory (1997–2002).
The exposure history of cases of incident hepatitis C were collected in New South Wales, the Northern Territory, South Australia, Tasmania, Victoria and Western Australia in 2007 (Table 10). Approximately 77% of these hepatitis cases were among people with a history of injecting drug use. In eight of the cases the only reported risk factor was having been born to a woman with hepatitis C infection.
Table 10: Incident hepatitis C infection, Australia,* 2007, by exposure category†
Exposure category |
Number | Percentage |
|---|---|---|
| Injecting drug use | 207 |
77.5 |
| Sexual contact | 7 |
2.6 |
| Blood/tissue recipient | 3 |
1.1 |
| Skin penetration procedure | 4 |
1.5 |
| Healthcare exposure | 2 |
0.8 |
| Household contact | 0 |
0 |
| Other‡ | 14 |
5.2 |
| Undetermined | 30 |
11.3 |
| Total exposures | 267 |
100.0 |
Source: National Centre in HIV Epidemiology and Clinical Research.4
* Includes diagnoses in New South Wales, the Northern Territory, South Australia, Tasmania, Victoria, and Western Australia.
† More than 1 exposure category for each case may be recorded.
‡ Includes 8 cases for which the only reported risk factor was having been born to a woman with hepatitis C infection.
Hepatitis C (unspecified) notifications
In 2007, 11,977 hepatitis C (unspecified) infections were notified to the NNDSS, representing 57.0 cases per 100,000 population (11,972 cases and 57.8 cases per 100,000 population in 2006).
The national notification rate for hepatitis C (unspecified) infection declined from 106.0 cases per 100,000 population in 1999 to 58.8 cases per 100,000 population in 2005 and has remained stable between 2005 and 2007 (range 57.0–58.8 cases per 100,000 population) (Figure 9). Improved surveillance practices, such as more complete follow-up and classification of incident cases; increased duplicate notification checks; and the Northern Territory separately reporting incident hepatitis C notifications from 2003, may account for some of the decrease in hepatitis C (unspecified) notifications since 2000.
In 2007, the Northern Territory continued to have the highest notification rate (103.8 cases per 100,000 population), followed by Queensland (65.2 cases per 100,000 population), which includes both incident and unspecified cases; and New South Wales (60.8 cases per 100,000 population).
The sex of cases was reported in 11,923 of the 11,977 cases in 2007. Of these cases nationally, the male to female ratio was 1.7:1. The highest notification rate occurred in the 30–34 years age group (158.7 cases per 100,000 population) among males and in the 25–29 and 30–34 years age groups (94.0 and 88.9 cases per 100,000 population respectively) among females (Figure 12).
Figure 12: Notification rate for hepatitis C (unspecified) infection,* Australia, 2007, by age group and sex†
* Data provided from Queensland includes both incident and unspecified hepatitis C cases.
† Excludes 54 cases whose sex was not reported.
Trends in the age distribution of hepatitis C (unspecified) infection are shown in Figure 13. From 2003 to 2007, the notification rate for hepatitis C (unspecified) among the 15–19 years age group decreased by 67%. Between 2003 and 2007, notification rates fell on average by 9.1% per year among cases in the 20–29 years age group. In the 30–39 years age group, notification rates have also been declining, on average by 4.3% per year since 2003. The decline in the population rate of notifications of hepatitis C infection may be attributable to a reduction in the prevalence of risk behaviours related to injecting drug use, especially among young people, however, changes in the rates of testing and percentage classified as incident cases may also have contributed to the decline.
Figure 13: Notification rates for hepatitis C (unspecified) infection,* Australia, 1997 to 2007, by age group
* Data provided from Queensland (1997 to 2007) and the Northern Territory (1995 to 2002) includes both incident and unspecified hepatitis C cases.
Although initial infection with the hepatitis C virus may be asymptomatic (more than 90% of cases) or mildly symptomatic, a high percentage (50%–80%) of cases will develop a chronic infection. Of chronically infected persons, approximately 50% will eventually develop cirrhosis or cancer of the liver.4 In 2007, it is estimated that 278,000 people living in Australia, had been exposed to the hepatitis C virus. Of these people approximately 160,000 had chronic hepatitis C infection and early liver disease (stage F0/1), and 42,000 had chronic hepatitis C infection and moderate liver disease (stage F2/3) associated with chronic hepatitis C infection; 5,600 were living with hepatitis C related cirrhosis; and 68,500 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.4 People co-infected with hepatitis B and hepatitis D may have more severe acute disease and a higher risk of fulminant hepatitis compared to 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 group at risk for hepatitis D infection.
There were 34 notifications of hepatitis D to the NNDSS in 2007, compared with 31 notifications in 2006, giving a notification rate of 0.2 cases per 100,000 population. The male to female ratio was 2.4:1. Of the 34 notifications, 11 were reported from New South Wales, 10 from Victoria, 9 from Queensland and 4 from Western Australia.
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Communicable Diseases Surveillance
This issue - Vol 33 No 2, June 2009
NNDSS Annual report 2007
Communicable Diseases Intelligence