This article {extract} was published in Communicable Diseases Intelligence Vol 34 No 3 September 2010 and may be downloaded as a full version PDF from the Table of contents page.
Results, continued
Sexually transmissible infections
In 2008, the sexually transmissible infections (STIs) reported to NNDSS were chlamydial infection, donovanosis, gonococcal infection and syphilis. Other national surveillance systems that monitor STIs in Australia include the Australian Gonococcal Surveillance Programme (AGSP), which is a network of specialist laboratories monitoring antimicrobial susceptibility patterns of infection; and the NCHECR, which maintains the National HIV Registry and the National AIDS Registry.
Since 2004, 2 categories of non-congenital syphilis have been reported: infectious syphilis (primary, secondary and early latent) of less than 2 years duration; and syphilis of greater than 2 years or unknown duration. The NNDSS also received reports on cases of congenital syphilis. These conditions were notified in all states and territories, except in South Australia where cases of syphilis of greater than 2 years or unknown duration were not reported to the NNDSS.
The national trends in the number and rates of STI notifications reported to the NNDSS between 2003 and 2008 are shown in Table 7. In interpreting these data it is important to note that changes in notifications over time may not solely reflect changes in disease prevalence. Increases in screening rates,29, 30 more targeted screening, the use of less invasive and more sensitive diagnostic tests, as well as periodic public awareness campaigns may contribute to changes in the number of notifications over time. For some diseases, changes in surveillance practices may also need to be taken into account when interpreting national trends.
Indirect age standardised notification rates, using the method described by the Australian Institute of Health and Welfare,31 were calculated for Indigenous and non-Indigenous notifications for jurisdictions that had indigenous status data completed in more than 50% of notifications. Where the indigenous status was not completed, notifications were counted as non-Indigenous when analysing these notifications. These data however, need to be interpreted with caution as STI screening occurs predominately in specific high risk groups, including in Indigenous populations; and Indigenous and non-Indigenous population distributions and proportions vary widely for each jurisdiction. Previous research into high rates of STIs amongst the Indigenous population in the Northern Territory established that the disparity in notification rates could be attributed to more targeted screening programs and to poorer access to primary health care services, rather than increased levels of sexual activity amongst Indigenous people.32, 33 Similarly, rates between females and males need to be interpreted with caution as rates of testing for STIs and health care-seeking behaviours differ between the sexes.
Notifications of chlamydial, gonococcal and non-congenital syphilis infections were excluded from analysis where the case was aged 13 years or less and the infection was deemed to be non-sexually acquired, e.g. perinatally acquired infections.
Chlamydial infection
Chlamydial infection continues to be the most commonly notified disease in 2008. A total of 58,484 notifications of chlamydial infection were received, corresponding to a rate of 273 per 100,000 population. This represents an increase of 10% on the rate reported in 2007 (247 per 100,000 population). The rate of chlamydial notifications has continued to increase since surveillance of the condition commenced in 1991 in all jurisdictions, except New South Wales where it became notifiable in 1997. Between 2003 and 2008, chlamydial infection notification rates increased from 152.9 to 272.9 per 100,000 population, an increase of 78% (Table 7). While the prevalence of chlamydial infection varies by age group and other demographic and behavioural factors, no major section of the population is spared.34
Chlamydial infection notification rates were substantially higher than the national average in the Northern Territory (1,044 per 100,000 population), Western Australia (397.9 per 100,000 population) and Queensland (353.9 per 100,000 population) (Table 6). At a regional level, chlamydial notification rates were highest in the Barkly and Central NT Statistical Subdivisions of the Northern Territory (range: 1144.6 to 2121.1 notifications per 100,000 population), noting that notification rates in geographic areas where the estimated residential population and case numbers are small, should be interpreted with caution. In the Statistical Divisions of Far North in Queensland and Pilbara in Western Australia and the Northern Territory Statistical Subdivisions of Alligator, East Arnhem, Finniss and the Lower Top End NT, notifications rates were also substantially higher than the national rate (range: 740.9 to 1144.5 notifications per 100,000 population) (Map 2).
Map 2: Notification rates and counts* for chlamydial infection, Australia, 2008, by Statistical Division of residence and Statistical Subdivision of residence for the Northern Territory
* Numbers shown in the Statistical Divisions and Statistical Subdivisions represent the count of notifications.
Notification rates in geographic areas where estimated residential population and case numbers are small should be interpreted with caution.
In 2008, notification rates of chlamydial infection in males and females were 221.4 and 322.8 per 100,000 population respectively. When compared with 2007, notification rates increased by 11% in males and 10% in females. The male to female ratio in 2008 was 0.7:1, which is similar to previous years. Rates in females markedly exceeded those in males, especially in the 15–19 and 20–24 year age groups with ratios of 0.3:1 and 0.6:1 respectively (Figure 21).
Figure 21: Notification rate of chlamydial infection, Australia, 2008, by age group and sex*
* Excludes 114 notifications whose age or sex was not reported.
Trends in age and sex specific notification rates between 2003 and 2008 show increases across all age ranges, especially between 15 and 29 years in both males and females (Figure 22). Since 2003, the highest notification rate increases occurred in males in the 20–24 year age group (80%) and amongst females in the 15–19 (90%) and 20–24 year age groups (70%).
From 2003 to 2008 the rates of chlamydial infection diagnosis have increased in both Indigenous and non-Indigenous populations. Nationally in 2008, data on indigenous status were complete in 48% of notifications, higher than the preceding 5-year average of 43% (range: 40%–45%). Six jurisdictions had greater than 50% completeness of the indigenous status field: the Northern Territory, Queensland, South Australia, Victoria, Tasmania and Western Australia. Among these jurisdictions, the combined age standardised notification rate was 1,134 per 100,000 in the Indigenous population and 279 per 100,000 in the non-Indigenous population.
Figure 22: Trends in notification rates of chlamydial infection in persons aged 10–39 years, Australia, 2003 to 2008, by age group and sex
The age standardised rate ratio of Indigenous to non-Indigenous chlamydial infection notifications across these jurisdictions was 4:1. Between 2006 and 2008, rates of chlamydial infection notifications in the Indigenous population increased by 7% in the Northern Territory and decreased by 34% in South Australia for the same period (Figure 23). Nationally, the disparity in notification rates between Indigenous and non-Indigenous populations has improved substantially since 2000. It should be noted that indigenous status identification completeness in the notification data varies both across years and by jurisdiction.
Figure 23: Trends in notification rates of chlamydial infection, selected states and territories,* 2003 to 2008, by indigenous status
* States and territories in which Indigenous status completeness was reported for more than 50% of cases over a 5 year period.
Although surveillance data continue to show substantial increases in chlamydial infection notifications nationally, a large proportion of cases with genital chlamydial infections are asymptomatic.17 Enhanced surveillance of chlamydial notifications undertaken in Tasmania during 2008 identified that 57% of males presented as asymptomatic compared with 70% of females (personal communication, David Coleman, Tasmanian Department of Health and Human Services, 2 July 2010). A paper published on enhanced chlamydial surveillance data in Tasmania for the period 2001 to 2007 also noted that females were more likely to have been tested for chlamydial infection as a result of screening, and males were more likely to have been tested when presenting with symptoms or as a result of contact tracing.35 Therefore, notification rates for this disease are particularly susceptible to overall rates of testing as well as targeted testing in certain high risk population sub-groups.
Donovanosis
Donovanosis is a sexually transmissible infection characterised by a chronic ulcerative genital disease. Although it is now relatively uncommon, it is a disease of public health importance in Australia because it predominantly occurs in Indigenous communities and has been identified as a potential co-factor in HIV transmission. Donovanosis has been targeted for elimination in Australia through the National Donovanosis Elimination Project.36 In 2008, 2 notifications in Indigenous males, one from Queensland and one from the Northern Territory, were reported to the NNDSS, one fewer than in 2007 (Figure 24).
Figure 24: Number of notifications of donovanosis, Australia, 1991 to 2008, by sex
Gonococcal infections
In 2008, 7,723 notifications of gonococcal infection were received by the NNDSS corresponding to a rate of 36.0 per 100,000 population, a slight decrease compared with 2007 (36.4 per 100,000 population).
The highest notification rate in 2008 was in the Northern Territory (713 per 100,000 population), substantially higher compared with Western Australia, Queensland and South Australia (78.0, 38.1 and 32.5 per 100,000 population respectively) (Table 6). Considerable declines in notification rates between 2007 and 2008 were observed in the Australian Capital Territory (54%), Tasmania (35%) and Victoria (12%). Increases in notification rates for the same period were observed in South Australia (20%) and Queensland (16%).
Nationally, there was a decrease in the gonococcal infection notification rates in males (3%) and an increase in the notification rates in females (3%). Gonococcal infection notification rates were substantially higher amongst males than females, 47.1 and 25.0 per 100,000 population respectively. The male to female rate ratio in 2008 was 2:1, similar to the previous 5 years (2003 to 2007). As in previous years, the exception to this pattern was the Northern Territory, where females had an overall higher notification rate than males (748 versus 677 per 100,000 population). Nationally, notification rates of gonococcal infection in males exceeded those in females in all age groups except in the 10–14 and 15–19 year age groups (Figure 25).
Figure 25: Notification rate of gonococcal infections, Australia, 2008, by age group and sex*
* Excludes 12 notifications whose age or sex was not reported.
Trends in sex specific notification rates show that in 2008 there has been an abatement of the declines seen in 2007 amongst males in the 20–34 year age range. In females, there were no marked change in notification rates; trends for all age groups appeared to remain relatively stable with a small increase occurring in the 15–19 year age group and a decrease continuing to occur in the 20–24 year age group (Figure 26).
Figure 26: Trends in notification rates of gonococcal infection in persons aged 10–44 years, Australia, 2003 to 2008, by age group and sex
In 2008, the data completeness of the indigenous status field for gonococcal infection notifications was 72%, which is a slight increase compared with previous years. Six jurisdictions had greater than 50% completeness of the indigenous status field: the Northern Territory, Queensland, South Australia, Tasmania, Victoria and Western Australia. Among these jurisdictions the combined age standardised notification rate for gonococcal infection was 791 per 100,000 in the Indigenous population and 21 per 100,000 in the non-Indigenous population. The age standardised rate ratio of Indigenous compared with non-Indigenous gonococcal infection notifications across these respective jurisdictions was 37:1. Between 2007 and 2008, rates of gonococcal infection notifications in the Indigenous population declined by 32% in South Australia, with declines also being seen in the Northern Territory, Tasmania and Western Australia. For the same period, increases in the notification rate of gonococcal infections were seen in Queensland (17%). In Victoria, there was a doubling of the rate, however this effect was due to changes in very small notification numbers in this population (Figure 27).
Figure 27: Trends in notification rates of gonococcal infection, selected states and territories,* 2003 to 2008, by indigenous status
* States and territories in which indigenous status completeness was reported for more than 50% of cases over a 5 year period.
Other surveillance of gonococcal infections
The AGSP is the national surveillance system for monitoring the antimicrobial resistance of Neisseria gonorrhoeae isolates, via a network of public and private reference laboratories located in each jurisdiction. Susceptibility testing is performed on gonococcal isolates to a core group of antibiotics: penicillin, ceftriaxone, spectinomycin, quinolone and tetracycline, using a standard methodology. The following is a summary of the AGSP 2008 report.37
In 2008, a total of 3,192 gonococcal isolates were tested for antibiotic susceptibility, representing approximately 41% of gonococcal infection notifications. The number of gonococcal isolates available for susceptibility testing is affected by the increasing use of non-culture based diagnosis methods.
Of the total number of isolates collected through the AGSP in 2008, there were 2,509 isolates from males, 682 isolates from females (male to female ratio 4.7:1) and there was 1 isolate where the sex was not reported. In males, 73% of isolates were obtained from the urethra, 15% from the rectum and 9% from the pharynx. In females, the majority of isolates (88%) were obtained from the cervix.
In 2008, approximately 44% of gonococcal isolates were resistant to penicillins and 54% to the quinolone antibiotic group. The number of isolates with high level tetracycline resistance continued to be at a historically high level. As in previous years, the pattern of gonococcal antibiotic susceptibility differed between states and territories, and rural and urban areas within each jurisdiction,38 where for example in remote areas of some jurisdictions with high disease rates, penicillin based treatments continue to be effective.
Syphilis (all categories)
In 2004, all jurisdictions began reporting to the NNDSS non-congenital syphilis infections categorised as: infectious syphilis (primary, secondary or early latent) of less than 2 years duration; and syphilis of more than 2 years or unknown duration. However, in South Australia only notifications of infectious syphilis are reported to the NNDSS. Detailed analyses are reported for these 2 categories, as well as for syphilis of the combined categories (syphilis – all categories) for the purpose of showing trends in previous years.
In 2008, a total of 3,243 notifications of syphilis infection of all categories was reported, representing a notification rate of 15.1 per 100,000 population, a slight increase compared with 2007 (Table 7, Figure 28). The Northern Territory continued to have the highest notification rate of syphilis (115 per 100,000 population), although in 2008 the rate was 17% lower than in 2007. In 2008, there were increases in notification rates in Western Australia (30%), the Australian Capital Territory (27%), New South Wales (14%) and South Australia (5%). As in other developed countries syphilis infection rates have continued to rise in Australia amongst men who have sex with men.39,40
Figure 28: Notification rate of non-congenital syphilis infection (all categories), Australia, 2003 to 2008
Syphilis – infectious (primary, secondary and early latent), less than 2 years duration
In 2008, a total of 1,303 cases of infectious syphilis (primary, secondary and early latent), less than 2 years duration, were reported. This represents a notification rate of 6.1 per 100,000 population, a decrease of 9% compared with 2007 (6.7 per 100,000 population) (Table 7). The Northern Territory had the highest notification rate at 37.8 per 100,000 population in 2008, a decrease of 32% compared with 2007. Decreases in notification rates per 100,000 population compared with 2007 occurred across all jurisdictions, except Western Australian and South Australia, which increased by 69% (4.9 to 8.3) and 5% (3.1 to 3.2) respectively.
Nationally, the notification rates of infectious syphilis for males and females were 10.8 and 1.4 per 100,000 population respectively, and represented a male to female ratio of 8:1 (Table 14). Notification rates in males were highest in the 35–39 year age group (27.1 per 100,000 population), closely followed by the 40–44 year age group (25.3 per 100,000), whereas in females the highest notification rate was observed in the 15–19 year age group (5.2 per 100,000 population). In all jurisdictions and across all age groups, notification rates were higher in males than in females, except the 10–14 year age group where the rate was 1.2 per 100,000 for females compared with no notifications for males (Figure 29).
Table 14: Number and rates* of notifications of infectious syphilis (less than 2 years duration), Australia, 2008, by state or territory and sex†
State or territory |
Male | Female | Total | |||
|---|---|---|---|---|---|---|
| Count | Rate* | Count | Rate* | Count | Rate* | |
| ACT/NSW | 398 |
11.0 |
22 |
0.6 |
420 |
5.7 |
| NT | 49 |
43.0 |
34 |
32.1 |
83 |
37.8 |
| Qld | 167 |
7.8 |
20 |
0.9 |
187 |
4.4 |
| SA | 45 |
5.7 |
7 |
0.9 |
52 |
3.2 |
| Tas | 5 |
2.0 |
2 |
0.8 |
7 |
1.4 |
| Vic | 355 |
13.5 |
17 |
0.6 |
374 |
7.0 |
| WA | 133 |
12.1 |
47 |
4.4 |
180 |
3.4 |
| Total | 1,152 |
10.8 |
149 |
1.4 |
1,303 |
6.1 |
* Notification rate per 100,000 population.
† Total includes 2 notifications whose sex was not reported.
Figure 29: Notification rate of infectious syphilis (primary, secondary and early latent), less than 2 years duration, Australia, 2008, by age group and sex
* Excludes 2 notifications whose sex was not reported.
Over the period 2004 to 2008 notification rates amongst males increased substantially until 2007, especially in the 20–29, 30–34 and 40–49 year age groups, and then decreased or were similar in 2008. The overall increases observed during this period occurred mainly in men who have sex with men.4 In females, for the 2004 to 2008 period, rates remained relatively steady, except in the 15–19 and 20–29 year age groups where they decreased by 21% and 41%, respectively, compared with 2007 (Figure 30).
Figure 30: Trends in notification rates of infectious syphilis (primary, secondary and early latent), less than 2 years duration, in persons aged 10 years or over, Australia, 2004 to 2008, by age group and sex
In 2008, data on indigenous status were complete in 96% of notifications of infectious syphilis and all jurisdictions had greater than 50% completeness of the indigenous status field. The age standardised notification rate was 37.1 per 100,000 in the Indigenous population and 5.3 per 100,000 in the non-Indigenous population, representing a ratio of 7:1. These age standardised notification rates ranged substantially across jurisdictions. Over the past 5 years, the disparity in notification rates between Indigenous and non-Indigenous populations continued to decrease across all jurisdictions except the Australian Capital Territory (indigenous status less than 50% complete 2004–2007) (Figure 31). Analysis of age specific notification rates show that compared with the non-Indigenous population, rates of infectious syphilis in the Indigenous population are highest in a younger age group, 15–19 years, compared with the non-Indigenous population where notification rates are highest in the 35–39 year age group.
Figure 31: Trends in notification rates of infectious syphilis, selected states and territories,* 2003 to 2008, by indigenous status
* States and territories in which Indigenous status completeness was reported for more than 50% of cases over a 5 year period.
Syphilis of more than 2 years or unknown duration
In 2008, a total of 1,940 notifications of syphilis of more than 2 years or unknown duration were reported, a notification rate of 9.8 per 100,000 population. This rate represents an increase of 10% compared with 2007 (8.9 per 100,000 population). The Northern Territory continued to have the highest notification rate at 77.3 per 100,000 population, however, this was a decrease of 6% compared with 2007 (81.9 per 100,000 population).
Table 15: Number and rates* of notifications of syphilis of more than 2 years or unknown duration, Australia,† 2008, by state or territory and sex
State or territory |
Male | Female | Total‡ | |||
|---|---|---|---|---|---|---|
| Count | Rate* | Count | Rate* | Count | Rate* | |
| ACT/NSW | 715 |
19.7 |
304 |
8.2 |
1,023 |
14.0 |
| NT | 84 |
73.7 |
86 |
81.3 |
170 |
77.3 |
| Qld | 115 |
5.4 |
88 |
4.1 |
203 |
4.7 |
| Tas | 11 |
4.5 |
4 |
1.6 |
15 |
3.0 |
| Vic | 273 |
10.4 |
139 |
5.2 |
419 |
7.9 |
| WA | 59 |
5.4 |
51 |
4.8 |
110 |
2.1 |
| Total | 1,257 |
12.7 |
672 |
6.7 |
1,940 |
9.8 |
* Notification rate per 100,000 population.
† Data from all states and territories except South Australia.
‡ Total includes 10 notifications whose sex was not reported.
In 2008, notification rates of syphilis of more than 2 years or unknown duration in males and females were 12.7 and 6.7 per 100,000 population, respectively (Table 15). Notification rates were higher in males than in females in all jurisdictions, except the Northern Territory, where males had a lower rate than females (74 and 81 per 100,000 population, respectively). Nationally, the male to female ratio was 1.9:1. The distributions of notification rates across age groups were similar in males and females with a bimodal distribution, noting however, that rates in males were substantially higher compared with females, especially in the older age groups. In males, the rate remained high from 35 years and over, peaking in the 35–49 year age range and again in the 85 or over year age group. Whilst amongst females, a younger peak was seen in the 30–34 year age group, with a second peak again in the 85 years or over age group (Figure 32).
Figure 32: Notification rate of syphilis of more than 2 years or unknown duration, Australia,* 2008, by age group and sex†
* Data from all states and territories except South Australia.
† Excludes 11 notifications where sex was not reported.
Over the period 2004 to 2008, notification rates increased substantially between 2005 and 2008 amongst males aged 30 years or over. In females for the same period, notification rates have remained relatively stable, except in females aged 20–29 years where the rates have decreased from 14 per 100,000 population in 2004 to 8 per 100,000 population in 2008 (Figure 33).
Figure 33: Rates of notification of syphilis of more than 2 years or unknown duration, Australia,* 2004 to 2008, by age group and sex
* Data from all states and territories except South Australia.
Congenital syphilis
There were 7 notifications of congenital syphilis reported in 2008, 3 males and 4 females. Three notifications each were reported from New South Wales and Queensland, and one from the Northern Territory. Two of the notifications were Indigenous, four non-Indigenous and one was reported as unknown indigenous status. Following a peak of 19 notifications in 2001, notifications of congenital syphilis have continued to decline (Figure 34).
Figure 34: Trends in notifications of congenital syphilis, Australia, 1999 to 2008
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Communicable Diseases Surveillance
This issue - Vol 34 No 3, September 2010
NNDSS Annual report 2008
Communicable Diseases Intelligence