A print friendly PDF version is available from this Communicable Diseases Intelligence issue's table of contents.

Bloodborne infections

Introduction

In 2000, bloodborne viruses (BBV) reported to the NNDSS included hepatitis B, C, D and hepatitis 'not elsewhere classified' (NEC). Newly acquired hepatitis C virus (HCV) and hepatitis B virus (HBV) infections (incident) were differentiated from those where the timing of disease acquisition is unknown (unspecified). 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.

As considerable time may have elapsed between onset and report date for chronic hepatitis infections, the analysis of unspecified HBV and unspecified HCV infections in the following sections is by report date, rather than by onset date.

In 2000, bloodborne virus infections accounted for 28,341 notifications to the NNDSS, which was 31.6 per cent of the total notified cases.

The overall trends in the number of notifications and rates for bloodborne viruses reported to the NNDSS since 1991 are shown in Tables 4 and 5. Hepatitis C remains the most commonly notified BBV in Australia. While most of the BBV show an increase in the total number of notifications across this reporting period, the increases are likely to reflect changes in surveillance practices rather than a true change in disease activity. Changes in surveillance are discussed on a disease by disease basis in the following sections. Only the reporting of hepatitis NEC has decreased over time, probably due to improved classification into the other hepatitis groups.

Table 4. Trends in notifications of bloodborne viruses, Australia, 1991 to 2000^*†

Disease	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000
Hepatitis B (incident)	-	-	-	283	271	212	269	265	303	395
Hepatitis B (unspecified)	3,469	4,847	5,282	5,394	4,434	5,580	6,542	6,562	7,164	7,908
Hepatitis C (incident)	-	-	25	26	77	71	154	350	396	441
Hepatitis C (unspecified)	-	-	-	-	17,154	17,674	17,290	18,075	18,655	19,569
Hepatitis D	-	-	-	-	-	-	-	-	19	27
Hepatitis (NEC)	253	34	33	23	12	15	6	4	0	1

* Notifications of hepatitis B (unspecified) and hepatitis C (unspecified) were analysed by report date.
† All jurisdictions reported for all years with the following exceptions:
Hepatitis B (incident) not reported from the Australian Capital Territory (1994)
Hepatitis B (unspecified) not reported from the Northern Territory (1991 to 2000)
Hepatitis C (incident) not separated from hepatitis C (unspecified) in Queensland or the Northern Territory (1991 to 2000)
Hepatitis D not reported from Western Australia
Hepatitis (NEC) not reported from Western Australia

Top of pageTable 5. Trends in notification rates of bloodborne viruses, Australia, 1991 to 2000^*† (rate per 100,000 population)

Disease	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000
Hepatitis B (incident)	-	-	-	1.6	1.5	1.2	1.5	1.4	1.6	2.1
Hepatitis B (unspecified)	20.3	28.0	30.2	30.5	24.8	30.8	35.7	35.4	38.2	41.7
Hepatitis C (incident)	-	-	0.2	0.2	0.5	0.5	1.0	2.3	2.6	2.9
Hepatitis C (unspecified)	-	-	-	-	94.9	96.5	93.4	96.5	98.4	102.2
Hepatitis D	-	-	-	-	-	-	-	-	0.1	0.2
Hepatitis (NEC)	1.6	0.2	0.2	0.1	0.1	0.1	< 0.1	< 0.1	0.0	< 0.1

* Notifications of hepatitis B (unspecified) and hepatitis C (unspecified) were analysed by report date.
† All jurisdictions reported for all years with the following exceptions:
Hepatitis B (incident) not reported from the Australian Capital Territory (1994).
Hepatitis B (unspecified) not reported from the Northern Territory (1991 to 2000).
Hepatitis C (incident) not separated from hepatitis C (unspecified) in Queensland or the Northern Territory (1991 to 2000).
Hepatitis D not reported from Western Australia.
Hepatitis (NEC) not reported from Western Australia.

Hepatitis B

In the early 1990s incident and unspecified hepatitis B notifications were not reported separately by most jurisdictions. Since 1994, all jurisdictions have reported incident cases of hepatitis B to the NNDSS. The overall trend in incident HBV notification rates between 1994 and 2000 shows a relatively stable reporting rate, between 1-2 cases per 100,000 population.

In total, 395 incident cases of hepatitis B were reported to the NNDSS with an onset date in 2000, giving a national notification rate of 2.1 cases per 100,000 population for this year. This represents an increase from the 303 incident cases reported in 1999 (1.6 cases per 100,000 population), with the most notable increases in the number of notifications from Western Australia, Tasmania and New South Wales. In 2000, the highest rates were reported from Western Australia (3.8 cases per 100,000 population), Tasmania (3.8 cases per 100,000 population) and the Northern Territory (3.1 cases per 100,000 population). The majority of incident hepatitis B notifications were in the 20-24 year age group (Figure 5). Overall, infections in males exceeded those in females (male to female ratio of 1.6:1).

Figure 5. Notification rates of incident hepatitis B infections, Australia, 2000 by age and sex



Risk factor information for incident HBV infection was available from four jurisdictions, the Australian Capital Territory, South Australia, Tasmania and Victoria and is summarised in Table 6. The following analyses refer only to incident HBV cases reported in these jurisdictions in 2000, thus the jurisdictional totals reported below may vary from the analysis by onset date.

Top of pageTable 6. Risk factors identified in notifications of incident hepatitis B virus infections, 2000, Australia, by reporting State or Territory

Risk factor	Australian Capital Territory		South Australia		Tasmania		Victoria
	N	%	n	%	n	%	n	%
Injecting drug user*	3	100	15	50	11	61	65	57
Sexual contact with HBV case	0	0	5	17	0	0	31	27
Household/other contact	0	0	2	6	1	5	1	1
Overseas travel	0	0	3	10	0	0	0	0
Occupational	0	0	0	0	0	0	1	1
Other	0	0	0	0	3	17	0	0
None identified	0	0	5	17	3	17	16	14
Total	3	100	30	100	18	100	114	100

* Injecting drug users may have multiple risk factors for HBV infection

Unspecified hepatitis B notifications have been reported to the NNDSS by all jurisdictions except the Northern Territory since 1997. The notification rate has remained stable between 1997 and 2000, at around 40 cases per 100,000 population (Table 5). In 2000 there were 7,908 unspecified HBV cases notified, at a rate of 41.7 cases per 100,000 population (Tables 4 and 5). This rate is consistent with that recorded in 1999 (38.2 cases per 100,000 population). The male to female ratio for unspecified HBV cases reported in 2000 was 1.2:1. By jurisdiction, the highest rates of notification were in New South Wales (60.2 cases per 100,000 population), Western Australia (42.6 cases per 100,000 population) and Victoria (41.2 cases per 100,000 population). The highest rates were in the 35-39 year age group for men (91.4 cases per 100,000 population) and in the 30-34 year age group for women (79.1 cases per 100,000 population, Figure 6).

Figure 6. Notification rates of unspecified hepatitis B infections, Australia, 2000, by age and sex



Figure 6 indicates a small number of unspecified HBV cases reported in the 0-4 age group. Some of these cases may be perinatally acquired (particularly in 0-1 year olds), and could be reported as incident cases if the timing of infection is known to be at birth.

While free universal neonatal vaccination was introduced in the Northern Territory in 1990, prior to 1997 most other jurisdictions only vaccinated infants from ethnic groups with a high hepatitis B carriage rate, or those born to known HBV positive mothers. In 1997 there was an interim recommendation that universal vaccination of infants at birth be introduced, and in 2000, with the availability of combination vaccines, DTPa-hepB vaccine was included in the childhood immunisation schedule. Continued surveillance is essential to measure the impact of this vaccination program.

Hepatitis C

Hepatitis C infection has been notifiable in most Australian jurisdictions since 1991 (Table 7). The total number of unspecified hepatitis C notifications has remained stable since 1994 at around 15,000-20,000 cases per annum.

Table 7. Trends in notifications of unspecified hepatitis C virus infections, Australia 1991 to 2000, by State or Territory and date of report

Year	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
1991	59	657	10	1,491	NR	NR	1,667	NR	3,884
1992	110	3,761	93	2,702	NR	NR	1,262	NR	7,928
1993	244	5,640	212	2,670	NR	NR	2,659	1,106	12,531
1994	308	7,564	301	2,990	NR	NR	3,523	1,305	15,991
1995	330	6,782	301	2,808	1,026	274	4,506	1,127	17,154
1996	267	7,318	216	2,796	1,075	291	4,597	1,114	17,674
1997	315	6,775	295	2,843	835	234	4,940	1,053	17,290
1998	290	6,759	233	2,921	795	275	5,681	1,121	18,075
1999	282	6,780	191	3,046	854	310	6,165	1,027	18,655
2000	212	7,265	183	3,395	788	335	5,730	1,661	19,569

NR not reported

In 2000, there were 19,569 unspecified hepatitis C infections reported to the NNDSS, a notification rate of 102.2 cases per 100,000 population, slightly higher than the 98.4 cases per 100,000 population reported in 1999. Of the total notifications of unspecified hepatitis C, 37 per cent of the notifications were from New South Wales. The highest notification rates were from Victoria (120.2 cases per 100,000 population) and New South Wales (112.4 cases per 100,000 population). The male to female ratio was 1.8:1. The highest notification rates were in the 25-29 year age group for males (279.7 cases per 100,000 population) and in the 20-24 year age group for females (159.9 cases per 100,000 population, Figure 7).

Top of pageFigure 7. Notification rates of unspecified hepatitis C infections, Australia, 2000, by age and sex



Similarly to HBV, there were a number of HCV notifications in the 0-4 age group (Table 8) which could be classified as incident if perinatally acquired.

Table 8. Trends in notifications of hepatitis C virus infections in the 0-4 age group, Australia, 1997 to 2000

Year	Incident HCV infections*	Unspecified HCV infections†	Total
1997	0	167	167
1998	5	573	578
1999	1	105	106
2000	1	97	98

* By date of onset.
† By date of report.

Incident cases of hepatitis C have been separately notifiable since 1997 in all jurisdictions except the Northern Territory and Queensland (Table 9). It is recognised that the number of notifications vastly underestimates the true incidence of hepatitis C in Australia. The increase in incident hepatitis C notifications to the NNDSS should not necessarily be interpreted as evidence of increasing transmission in the Australian community. Instead the increase in the number of incident HCV notifications is largely a product of improved surveillance, increased awareness, and more widespread testing.

Table 9. Trends in notifications of incident hepatitis C virus infections, by State or Territory, 1993 to 2000

Year	ACT	NSW	SA	Tas	Vic	WA	Aust
1993	NR	23	NR	NR	NR	2	25
1994	6	20	NR	NR	NR	0	26
1995	8	33	33	2	NR	1	77
1996	8	19	28	4	NR	12	71
1997	3	19	48	2	9	73	154
1998	8	110	67	18	21	126	350
1999	20	100	80	18	70	108	396
2000	20	139	89	31	87	75	441

NR not reported

The numbers of incident cases detected are likely to be affected by the surveillance methods.¹⁶ In the larger jurisdictions classification of incident cases is determined by passive reporting. In smaller jurisdictions, where all (or the majority) of hepatitis C notifications were actively investigated to determine if they were incident or prevalent during this time period, a much higher proportion of incident cases was reported.

In total there were 441 incident cases of hepatitis C reported with an onset date in 2000, giving a rate of 2.9 cases per 100,000 population. The proportion of all HCV notifications that were known to be incident cases was 2.2 per cent in 2000, similar to the proportion in 1999 (2.1%), but reflecting the upward trend in this proportion since 1993. The highest rates of incident hepatitis C infection were reported from Tasmania (6.6 cases per 100,000 population), the Australian Capital Territory (6.4 cases per 100,000 population) and South Australia (5.9 cases per 100,000 population).The majority of incident hepatitis C notifications were in the 20-24 year age group (Figure 8).

Top of pageFigure 8. Notification rates of incident hepatitis C infections, Australia, 2000, by age and sex



In 2000, additional data were collected on incident hepatitis C infections in the Australian Capital Territory, the Northern Territory, South Australia, Tasmania and Victoria (M. Robotin, NCHECR, personal communication). The following analyses refer only to incident hepatitis C cases reported in these jurisdictions in 2000, thus the jurisdictional totals reported below may vary from the analysis by onset date.

Demographic profile of incident hepatitis C cases

The age and sex of incident hepatitis C cases notified in 2000 are summarised in Table 10, according to the State or Territory of diagnosis.

Table 10. Demographics of incident hepatitis C cases reported in the Australian Capital Territory, the Northern Territory, South Australia, Tasmania and Victoria, 2000

	ACT (n=20)	NT (n=5*)	SA (n=88)	Tasmania (n=27)	Victoria (n=77)
% males	11/20 (55%)	3/5 (60%)	45/88 (51%)	13/27 (48%)	41/77 (57%)
Median age in years (range)
Males	24 (22-39)	32 (28-45)	26 (18-45)	26 (18-48)	23 (15-42)
Females	28 (17-28)	37 (27-47)	24 (15-50)	28 (17-36)	22 (14-39)

* Since enhanced surveillance commenced in July 2000.

Method of diagnosis of incident hepatitis C

The basis of diagnosis was seroconversion in 72 per cent, clinical hepatitis in 23 per cent or a combination in 4 per cent of cases.

Reason for testing or reporting source

The reason for testing or the reporting source was recorded in three jurisdictions (the Northern Territory, Tasmania and Victoria). While no direct comparison can be made, as varying reasons were investigated in each jurisdiction, drug and alcohol screening was the major reason for testing in Tasmania (accounting for 44% of cases) and Victoria (27% of cases), while the investigation of symptoms was the major reason for testing in the Northern Territory (accounting for 60% of cases).

Exposure assessment for incident hepatitis C infections

Information on exposure assessment was available from four jurisdictions (the Australian Capital Territory, the Northern Territory, Tasmania and Victoria). Injecting drug use was the most common mode of transmission, accounting for 60 per cent of cases in the Northern Territory, 70 per cent of cases in the Australian Capital Territory, 74 per cent of cases in Tasmania and 86 per cent of cases in Victoria. Less common modes of transmission (for example, via tattoos, sexual exposure, iatrogenic exposure) were documented, although multiple exposures were not always recorded in each jurisdiction. In jurisdictions where multiple exposures were recorded, the majority were associated with injecting drug use.

Hepatitis D

Hepatitis D is an unusual virus as it uses the hepatitis B surface antigen in its own replication, and therefore requires co-infection with HBV.¹⁷ Infection can occur concurrently with HBV, or can occur as a superinfection, providing the individual is a HBV carrier.

There were 27 notifications of hepatitis D to the NNDSS in 2000 at a notification rate of 0.2 cases per 100,000 population. Of the 27 notifications, 12 were reported from Victoria, 10 from New South Wales and 5 from Queensland. The majority (85%) of notifications were from males, with the highest rate reported in 30-34 year age group (0.9 cases per 100,000 population).


This article was published in Communicable Diseases Intelligence Volume 26, No 2, June 2002