This article {extract} was published in Communicable Diseases Intelligence Vol 30 No 1 March 2006 and may be downloaded as a full version PDF from the Table of contents page.
Results, continued
Bloodborne diseases
In 2004, bloodborne viruses reported to the NNDSS included 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: http://www.med.unsw.edu.au/nchecr
When reported to NNDSS, newly acquired (incident) hepatitis B and hepatitis C infections were differentiated from those where the timing of disease acquisition was unknown (unspecified). As considerable time may have elapsed between the date of disease acquisition and the date an unspecified hepatitis infection is first diagnosed, the analysis of hepatitis B (unspecified) and hepatitis C (unspecified) infections is by date of diagnosis, which is the earliest of specimen, notification or notification received dates supplied.
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 2004, 275 incident hepatitis B infections were reported to the NNDSS, giving a national notification rate of 1.4 cases per 100,000 population. The highest rates were reported from the Northern Territory (4 cases per 100,000 population) and Tasmania (3.7 cases per 100,000 population). The rate of notification of incident hepatitis B infection increased from 1.5 in 1995 to 2.2 in 2002 and declined to 1.4 per 100,000 population in 2004 (Figure 5).
The increased rates of newly acquired hepatitis B infection in 2000–2002 were attributed to increased transmission among injecting drug users in Victoria, followed by a decline in transmission between 2002 and 2004 during a heroin 'drought' (Greg Dore, personal communication).
Figure 5. Trends in notification rates incident hepatitis B and hepatitis B (unspecified), Australia, 1995 to 2004*
* Year of onset for incident hepatitis B and year of report for hepatitis B (unspecified) notifications.
In 2004, the highest rate of incident hepatitis B infection was in the 20–24 year age group for females (4.8 cases per 100,000 population) and in the 30–34 year age group for males (4.2 cases per 100,000 population, Figure 6). Overall, infections in males exceeded those in females, with a male to female ratio of 1.4:1.
Figure 6. Notification rate for incident hepatitis B infections, Australia, 2004, by age group and sex
Trends in incident hepatitis B infection by year and age group are shown in Figure 7.
Figure 7. Trends in notification rates of incident hepatitis B infections, Australia, 1995 to 2004, by age group
In the past five years, rates of incident hepatitis B notifications fell by 75 per cent among cases in the 15–19 year age group and by 38 per cent among cases in the 20–24 year age group. The reported source of exposure for cases of incident hepatitis B infection in 2004 was reported from South Australia, Tasmania and Victoria (Table 5).
Table 5. Incident hepatitis B infection, Australia,* 2004, by exposure category
Exposure category |
Number | Percentage |
|---|---|---|
| Injecting drug use | 74 |
52.8 |
| Sexual contact | 31 |
22.2 |
| Male homosexual contact | 1 |
|
| Heterosexual contact | 30 |
|
| Blood/tissue recipient | 0 |
|
| Skin penetration procedure | 0 |
|
| Healthcare exposure | 0 |
|
| Household contact | 1 |
0.7 |
| Other | 1 |
0.7 |
| Undetermined | 33 |
23.6 |
| Total | 140 |
100.0 |
* Data from South Australia, Tasmania and Victoria only, (National Centre in HIV Epidemiology and Clinical Research, 2005 2).
The proportion of newly acquired hepatitis B infections associated with injecting drug use increased from 44 per cent in 2002 to 53 per cent in 2004. By contrast, the proportion of newly acquired hepatitis B infections associated with sexual contact declined from 26 per cent in 2002 to 22 per cent in 2004.2
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 2004, 5,861 cases of hepatitis B (unspecified) infection were notified to NNDSS, giving a rate of 29.1 cases per 100,000 population. New South Wales (42.4 cases per 100,000 population) and Victoria (29.8 cases per 100,000 population) recorded the highest notification rates. The male to female ratio was 1.3:1. Among males, the highest notification rate was in the 35–39 year age group (63.3 cases per 100,000 population), whereas among females, the highest notification rate was in the 25–29 year age group (63.4 cases per 100,000 population, ( Figure 8). The rate of notification of hepatitis B (unspecified) infection increased from 19.4 in 1996 to 42.8 in 2000 and declined to 29.1 cases per 100,000 population in 2004 ( Figure 5).
Figure 8. Notification rate for hepatitis B (unspecified) infections, Australia, 2004, by age group and sex*
Trends in hepatitis B (unspecified) infection by age group and year are shown in Figure 5.
Figure 9. Trends in notification rates of hepatitis B (unspecified) infections, Australia, 1995 to 2004, by age group*
Rates of hepatitis B (unspecified) notifications in 2000–2004 fell by 49 per cent among cases in the 15–19 year age group, 27 per cent in the 20–29 year age range and 22 per cent in the 30–39 year age range. Rates in other age groups remained relatively stable.
In 2004, 28 cases of HBV infection (3 incident and 25 unspecified) in children in the 0–4 year age group were reported. Approximately 95 per cent of infants born in 2004 received hepatitis B vaccination in Australia.3
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. |
The number of incident hepatitis C notifications as a reflection of the incidence of hepatitis C in Australia should be interpreted with caution. It is known that the notification rate vastly underestimates the true incidence of hepatitis C.
A total of 361 incident cases of hepatitis C with an onset date in 2004 were notified, giving a rate of 2.3 cases per 100,000 population (Figure 10). The proportion of all hepatitis C notifications in 2004 that were documented as incident cases was 2.7 per cent. The highest rate of incident hepatitis C infection was reported from Western Australia (6.1 cases per 100,000 population).
Figure 10. Trends in notification rates, incident and hepatitis C (unspecified) infection, Australia, 1995 to 2004
In 2004, the highest rate of incident hepatitis C notification was in the 20–24 year age group for males (9.1 cases per 100,000 population) and the 25–29 year age group for females (6.3 cases per 100,000 population, Figure 7). Overall, the male to female ratio was 1.5:1.
Figure 11. Notification rate for incident hepatitis C infections, Australia, 2004, by age group and sex
Trends in the age distribution of incident hepatitis C infection are shown in Figure 12.
Figure 12. Trends in notification rates of incident hepatitis C infections, Australia, 1997 to 2004, by age group
The notification rates for incident hepatitis C declined from 2001 to 2004 by 62 per cent in the 15–19 year age group, 60 per cent in the 20–29 year age group and 50 per cent in the 30–39 year age group (Figure 8).
The exposure history of cases of incident hepatitis C was collected in the Australian Capital Territory, South Australia, Tasmania, Victoria and Western Australia in 2004 (Table 6). At least 70 per cent of incident hepatitis C infections in 2004 were among injecting drug users.
Table 6. Incident hepatitis C infection, Australia,* 2004, by exposure category
Exposure category |
Number | Percentage |
|---|---|---|
| Injecting drug use | 210 |
70.0 |
| Sexual contact | 13 |
4.3 |
| Blood/tissue recipient | 4 |
1.3 |
| Skin penetration procedure | 7 |
2.3 |
| Healthcare exposure | 2 |
0.6 |
| Household contact | 1 |
0.3 |
| Other | 9 |
3.0 |
| Undetermined | 54 |
18.0 |
| Total | 300 |
100.0 |
* Data from the Australian Capital Territory, South Australia, Tasmania, Victoria and Western Australia only, (National Centre in HIV Epidemiology and Clinical Research, 2005 2)
In 2004, an estimated 259,570 people were living with hepatitis C in Australia. Of these 65,300 people cleared their infection, 153,300 had chronic hepatitis C and early liver disease (stage 0/1), 32,800 had chronic hepatitis C infection and moderate liver disease (stage 2/3) and 8,160 were living with hepatitis C related cirrhosis.2
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. |
National notification rates of hepatitis C (unspecified) infection ranged between 96 and 104 cases per 100,000 population in 1995–2001. The national rate declined to 81.3 in 2002 and to 63.7 cases per 100,000 population in 2004 (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 2004, 12,667 hepatitis C (unspecified) infections were notified to NNDSS, giving a notification rate of 63 cases per 100,000 population. Of the total notifications of hepatitis C (unspecified), 39 per cent were from New South Wales, but the Northern Territory had the highest notification rate (135.6 cases per 100,000 population). The male to female ratio was 1.6:1. The highest reporting rates were in the 35–39 year age group for males (164 cases per 100,000 population), and in the 25–29 year age group for females (114.2 cases per 100,000 population, Figure 13).
Figure 13. Notification rate for hepatitis C (unspecified) infections, Australia, 2004, by age group and sex
Trends in the age distribution of hepatitis C (unspecified) infections are shown in Figure 14.
Figure 14. Trends in notification rates of hepatitis C (unspecified) infections, Australia, 1995 to 2004, by age group
Between 2000 and 2004, the notification rates of hepatitis C (unspecified) fell by 71 per cent among cases in the 15–19 year age group, suggesting declining hepatitis C incidence among young people with a history of injecting drug use. Notification rates of hepatitis C (unspecified) also fell in the same period by 47 per cent among cases in the 20–29 year age range and by 40 per cent in the 30–39 year age range. Rates in the other age groups have remained relatively stable during this period.
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 superinfection 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 27 notifications of hepatitis D to the NNDSS in 2004 giving a notification rate of 0.1 cases per 100,000 population. Of the 27 notifications, 14 were reported from New South Wales, 10 from Queensland and 3 from Victoria. The majority (19/27, 70%) of cases were males, with the highest number of cases reported in 40–44 and 45–49 year age groups.
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This issue - Vol 30 No 1, March 2006
NNDSS Annual report 2004
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