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Sexually transmitted infections

Sexually transmitted infections (STIs) remain a prevalent public health problem in Australia, despite efforts in prevention and education. In 2001, chlamydial infection, donovanosis, gonococcal infection and syphilis were nationally reportable to NNDSS, while chancroid and lymphogranuloma venereum were removed from NNDSS reporting. During 2001, a total of 27,817 STI notifications were received by NNDSS, which accounted for 27 per cent of all notifications.

A number of systems are involved in STI surveillance in Australia, including the NNDSS, the Laboratory Virology and Serology Reporting Scheme (LabVISE) (for chlamydia and syphilis) and specialist laboratory networks such as the Australian Gonococcal Surveillance Programme.⁴⁰ The NCHECR has an interest in STI surveillance, and have further analysed data from the NNDSS and other reporting sources in their annual surveillance report.⁴¹

The number of chlamydia and gonococcal infections reported in 2001 were the highest since 1991. Increases were also observed for donovanosis, while the number of syphilis notifications were at their lowest level since reporting commenced. Increases in some STIs may be due to higher rates of diagnosis, however, changes in surveillance methods may also account for some of the observed trends.

Chlamydial infection

The rate of chlamydial infections continued to increase in 2001 (Figure 25). During the year, a total of 20,026 notifications of chlamydial infection were received by NNDSS, an 18 per cent increase on the 17,018 cases reported in 2000. The notification rate for chlamydial infections in 2001 was 103 cases per 100,000 population, an increase from 88 cases per 100,000 population in 2000.

Figure 25. Trends in notification rates of chlamydial infection, Australia, 1994 to 2001, by year of onset



The increase in the number of chlamydial notifications occurred in all states and territories (Table 11). South Australia recorded the largest increase in 2001, of 37 per cent.

Top of pageTable 11. Trends in notifications of chlamydial infection, 1994 to 2001, by state or territory

Year	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
1994	88	NN*	737	2,444	727	5	1,318	834	6,179
1995	80	NN	520	2,414	768	283	1,317	1,025	6,439
1996	110	NN	670	3,266	1,024	293	1,559	1,444	8,390
1997	142	NN	629	3,508	1,005	249	2,115	1,591	9,302
1998	194	NN	791	4,076	1,024	202	2,569	2,071	11,490
1999	177	2,461	863	4,476	973	254	2,939	1,903	14,046
2000	244	3,555	1,000	4,932	1,023	332	3,335	2,597	17,018
2001	301	4,389	1,239	5,596	1,402	380	3,924	2,733	19,964
Increase from 2000 (%)	23.4	23.5	23.9	13.5	37.0	14.5	17.7	5.2	17.3

* Not notifiable

Notification rates vary widely between states and territories. The rates were above the national average in the Northern Territory (619.4 cases per 100,000 population), Queensland (153.9 cases per 100,000 population) and Western Australia (143.4 cases per 100,000 population, Map 3).

Map 3. Notification rates of chlamydial infection, Australia, 2001, by Statistical Division of residence



The overall notification rate was 82.7 cases per 100,000 population for males and 122.2 cases per 100,000 population for females in 2001. The male to female ratio was 1:1.5, which was similar to 2000. Chlamydia is predominantly a disease of young adults. Among the cases in 2001, 77 per cent were in adolescents and young adults between the ages of 15 and 29 years. Notification rates of chlamydia in females exceeded those of males in each age group, with the greatest differences occurring in the 10-14 year age group (male:female ratio 1:7.7) and the 15-19 year age group (male:female ratio 1:3.8). Rates according to age group and sex are shown in Figure 26.

Figure 26. Notification rates of chlamydial infection, Australia, 2001, by age group and sex



In 2001, the highest notification rate for females occurred in the 20-24 year age group (653.2 cases per 100,000 population), followed by the 15-19 year age group (565.3 cases per 100,000 population). These rates are 5.3 times and 4.6 times the national rate for women, in those aged 20-24 and 15-19 years respectively.

Trends in the sex distribution pattern for the 15-29 year age range since 1997 (Figure 27) show increases for all three age groups (15-19, 20-24, 25-29 years). The largest increases for chlamydia notifications were observed for females in the 15-19 and 20-24 year age groups and for males in the 25-29 years group.

Top of pageFigure 27. Trends in notification rates of chlamydial infection in persons aged 15-29 years, Australia, 1997 to 2001, by sex



There were 53 cases of chlamydia infection reported in children aged less than 10 years. All of these were cases of chlamydial conjunctivitis. Notifications were from all states and territories except South Australia and Tasmania.

Based on notifications from the Northern Territory, South Australia and Western Australia to NNDSS, the NCHECR have reported further details on chlamydial infection in Indigenous Australians. For these jurisdictions, Indigenous status was identified in 73 per cent of the notifications.⁴¹ In 2001, the estimated age standardised rate of chlamydial infection among Indigenous Australians was 880 cases per 100,000 population, compared with the rate of 117 cases per 100,000 population in non-Indigenous Australians. Trends in notification rates of chlamydia in Indigenous and non-Indigenous Australians between 1997 and 2001 are shown in Figure 28.

Figure 28. Trends in age-standardised notification rates of chlamydial infection, the Northern Territory, South Australia and Western Australia (combined), 1997 to 2001, by Indigenous status*

* Data for 2001 unfinalised
Source: NCHECR HIV/AIDS Annual surveillance report: 2001

Chlamydial infection is caused by Chlamydia trachomatis. The infection can be asymptomatic. It has been estimated that in about 80 per cent of females and 40 per cent of males the infections are asymptomatic, and can easily remain undiagnosed.⁴² It is difficult, therefore, to estimate the true burden of chlamydial infection in Australia. The disease is usually transmitted by vaginal intercourse or during oral or anal sex. Mother-to-child transmission can also occur during birth and may result in conjunctivitis or pneumonia in the newborn.

There may be a number of reasons for the increase in the number of chlamydial cases over the past decade. The increase may reflect the effect of chlamydia control campaigns that increase the rate of screening. The use of non-invasive tests (e.g. testing of urine) and more sensitive assays for chlamydial infection may increase the number of tests undertaken and the number of positive results. Enhanced surveillance activities by health authorities and greater awareness of the disease by health professionals may improve reporting.

If real, the continued increase in cases of chlamydia infection over the past decade, particularly among adolescents and young adults, is a cause for public health concern. Data on risk factors and evaluations of preventative programs may help understand disease transmission and deliver more comprehensive and effective control programs. In 2001 the Department of Human Services, Victoria, launched the Chlamydia Strategy for Victoria, 2001 - 2004 to address the continuing increase in chlamydial infections.⁴³

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Donovanosis

Donovanosis is a sexually transmissible infection caused by Calymmatobacterium granulomatis, a gram-negative pleomorphic bacillus. It is characterised by genital ulcerative lesions which may develop into a chronic ulcerative disease if untreated. Lesions may be extensive and extragenital, and may be associated with secondary bacterial infection. The mode of transmission of donovanosis is primarily through sexual contact, although it may also be acquired by a faecal route, or at birth by passage through an infected birth canal.⁴⁴

Internationally, donovanosis is endemic in tropical and sub-tropical areas, particularly PNG, central America, southern Africa and southern India.¹⁶ In Australia, the disease is rare in the general population. It is, however, more common in Indigenous communities in rural and remote areas of northern Australia.^45,46

Donovanosis was notifiable in all states and territories except South Australia in 2001. Among the notifiable STIs, donovanosis is the least commonly reported. NNDSS received a total of 42 notifications of donovanosis from the Northern Territory, Queensland and Western Australia in 2001, with a rate of 0.2 cases per 100,000 population.

The number of donovanosis cases in 2001 was twice that of 2000 (n=21). The increase of donovanosis notifications may be the result of the donovanosis eradication program, which includes enhanced surveillance in addition to the use of more sensitive and acceptable diagnostic assays, such as polymerase chain reaction.^47,48 Ultimately though, it should lead to eradication. As part of the program, in 2001 a project officer was employed in Western Australia, to raise awareness of donovanosis among health-care workers and communities in rural and remote areas of the State.

The highest group specific rates in 2001 were reported for females in the 15-19 year age group (0.8 cases per 100,000 population) and males in the 20-24 year age group (0.7 cases per 100,000 population) and with a male to female ratio of 1:1.8. Data on Indigenous status were available for all notifications and all but two cases were in Indigenous Australians.

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Gonorrhoea

Infection by Neisseria gonorrhoeae is transmitted from person to person through vaginal, anal, or oral sexual contact. The disease may also be transmitted to the new-born from the mother's birth canal to cause gonococcal ophthalmia neonatorum. Humans are the only host for the bacterium.

As with chlamydial infection, the number of notifications of gonococcal infection in Australia has increased over the last decade. The annual national notification rate of gonococcal infection has increased steadily from 16 cases per 100,000 population in 1993 to 32 cases per 100,000 population in 2001 (Figure 29). In 2001, a total of 6,158 notifications of gonococcal infection were reported nationally, an increase from the 5,801 reports received in 2000. The increase occurred in the Australian Capital Territory, New South Wales, the Northern Territory and Tasmania. The remaining states and territories showed a decrease in notifications in 2001.

Figure 29. Trends in notification rates of gonococcal infection, Australia, 1991 to 2001



The notification rate was higher than the national average in the Northern Territory and Western Australia, with a rate 22 times the national level in the Northern Territory in 2001. The notification rate of gonococcal infection in 2001 was 42.9 cases per 100,000 population for males and 20.4 cases per 100,000 population for females. As in previous years, the male to female ratio remains 2:1. The age group specific notification rate of gonococcal infection in females was higher than that in males in the 10-14 year age group (male:female ratio; 1:3.8) and the 15-19 year age group (male:female ratio 1:1.5), while higher rates were observed in males compared to females in all other adult age groups (Figure 30).

Top of pageFigure 30. Notification rates of gonococcal infection, Australia, 2001, by age group and sex



Trends in the sex-specific rates of gonococcal infection in persons aged 15-29 years over recent years all show a general increase. The increase was greatest for females in the 15-19 year group. The highest age group and sex-specific rates over time have been in males aged 20-29 years (Figure 31).

Figure 31. Trends in notification rates of gonococcal infection, in persons aged 15-29 years, Australia, 1991 to 2001, by sex



Increased testing, the availability of more sensitive diagnostic tests, and enhanced surveillance may account for some of the increase. True increases in disease may occur in some communities, such as men who have sex with men.^49,50 In the Northern Territory, increased screening for gonococcal infection through four sentinel practices in 2001 may also have increased notification rates. The use of polymerase chain reaction in place of culture for diagnosis in some areas may be reducing the number of gonococcal isolates that can be used to monitor antibiotic resistance.

There was wide geographical variation in the rate of notification of gonococcal infection. The highest rates of notification were reported in the Kimberley (1,580 cases per 100,000 population) and Pilbara (780 cases per 100,000 population) Statistical Divisions in northern Western Australia and in the Northern Territory (765 cases per 100,000 population) (Map 4).

Top of pageMap 4. Notification rates of gonococcal infection, Australia, 2001, by Statistical Division of residence



Based on the notifications from the Northern Territory, South Australia and Western Australia to NNDSS, the NCHECR reported further details on gonococcal infection in Indigenous Australians. ⁴¹ From these three jurisdictions, data on Indigenous status in 2001 were available for 87 per cent of notifications. The age standardised gonococcal notification rates were estimated to be 1,290 cases per 100,000 population in the Indigenous population, compared with 25 cases per 100,000 population in the non-Indigenous population. This represents an increase in gonococcal notification rates since 1999 for Indigenous Australians. The same trend was also observed in non-Indigenous Australians (Figure 32).

Figure 32. Trends in age-standardised notification rates of gonococcal infection, the Northern Territory, South Australia and Western Australia (combined), 1997 to 2001, by Indigenous status*

Source: NCHECR HIV/AIDS Annual surveillance report: 2001

Other surveillance activities for gonococcal infections

The Australia Gonococcal Surveillance Programme is the national laboratory-based surveillance system that monitors the antibiotic susceptibility of the gonococcus. The program is undertaken by a network of reference laboratories in each state and territory, which use an agreed and standardised methodology to quantitatively determine susceptibility of the organism to a core group of antibiotics. The annual results of the Australian Gonococcal Surveillance Programme have recently been published.⁵¹

In 2001, a total of 3,706 of gonococcal isolates were analysed by the Australian Gonococcal Surveillance Programme, an increase of five per cent on the previous year's total. The most common anatomical sites of isolates obtained for testing were from the urethra for males (80%) and from the cervix for females (92%). Rectal isolates, obtained only from males, comprised ten per cent of the isolates. Of the total number of isolates, 85 per cent were from men, and this ratio was little changed from 2000.

Table 12 presents trends in annual antibiotic resistance rates in Australia between 1998 and 2001. The proportion of isolates resistant to penicillin by chromosomally-controlled mechanisms increased from 10.6 per cent in 2000 to 15.3 per cent in 2001, but this rate is still less than the 22 per cent recorded in 1998. While the level of quinolone resistance in gonococci decreased slightly from the previous year, it became more widespread in Australia in 2001. Antibiotic susceptibility patterns varied considerably between regions and resistance to the penicillins remained high in larger urban centres.⁵¹

Table 12. Proportion of gonococcal isolates showing antibiotic resistance, Australia, 1998 to 2001

	Penicillin resistance (% resistant)		Quinolone resistance (% resistant)	High level tetracycline resistance (% resistant)
	Plasmid mediated resistance	Chromosomally mediated resistance
1998	5.3	21.8	5.2	NR
1999	7.4	14.3	17.2	7.9
2000	8.7	10.6	17.8	9.1
2001	7.5	15.3	17.5	9.4

NR Not recorded

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Syphilis

During 2001, 1,406 cases of syphilis were reported to the NNDSS. This represents a decrease of notifications for the second consecutive year and it was the lowest number of cases received by NNDSS since 1991. In Australia, all states and territories report syphilis (including primary, secondary and latent syphilis) and congenital syphilis separately, to NNDSS.

In 2001 the overall notification rate for syphilis was 8.4 cases per 100,000 population for males and 6.1 cases per 100,000 population for females. The male to female ratio was 1:0.7. The peak notification rate was reported in females in the 15-19 year age group (16.2 cases per 100,000 population). The disease is more common in females in their child-bearing years. In 2001, 75 per cent of the cases in females occurred in the 15-44 year age range. The highest age specific notification rate for males was in the 20-24 year age group (14.4 cases per 100,000 population, Figure 33). Since 1991, overall decreases in the syphilis notification rate have been clearly observed in the 15-29 year age range, for both males and females (Figure 34).

Figure 33. Notification rates of syphilis, Australia, 2001, by age group and sex



Figure 34. Trends in notification rates of syphilis, in persons aged 15-29 years, Australia, 1991 to 2001, by sex



The national notification rate for syphilis in 2001 was 7.3 cases per 100,000 population, a decrease from 9.3 cases per 100,000 population in 2000. Decreases were seen in the Australian Capital Territory, New South Wales and Queensland. Increases in the number of syphilis notifications cases in 2001 was reported in the other five states and territories. The increase may reflect a more active follow-up of suspected cases.⁵² Significant cleaning of syphilis notification data in some states and territories in 2001 has accounted for decreased numbers of notifications.

In 2001, there was wide geographical variation in notification rates for syphilis (Map 5). The highest rate occurred in Western Australia in the Kimberley Statistical Division (360.9 cases per 100,000 population).

Top of pageMap 5. Notification rates of syphilis, Australia, 2001, by Statistical Division of residence



There were 21 cases of syphilis in children aged less than one year (3 in New South Wales, 17 in the Northern Territory and 1 in Western Australia). All were confirmed as congenital syphilis.

Based on the notifications from the Northern Territory, South Australia and Western Australia to NNDSS, the NCHECR reported further details on syphilis in Indigenous Australians.⁴¹ From these three jurisdictions, data on Indigenous status was available for 93 per cent of notifications in 2001. The age standardised syphilis rates were estimated to be 394 cases per 100,000 population for Indigenous Australians, compared with 4 cases per 100,000 population for non-Indigenous Australians. Trends in notification rates of syphilis in Indigenous and non-Indigenous Australians from these states and territories between 1997 and 2001 are shown in Figure 35.

Figure 35. Trends in age-standardised notification rates of syphilis, the Northern Territory, South Australia and Western Australia (combined), 1997 to 2001, by Indigenous status*

* Data for 2001 unfinalised
Source: NCHECR HIV/AIDS Annual surveillance report: 2001.

This article was published in Communicable Diseases Intelligence Volume 27, No 1, March 2003.