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Sexually transmitted infections

The infections classified as sexually transmissible for surveillance in the NNDSS are chancroid, chlamydial infection, donovanosis, gonococcal infection, lymphogranuloma venereum and syphilis.

States and Territory health departments follow NHMRC case definitions for the reporting of these conditions (Appendix 1d).

There are important infections commonly or usually spread by sexual contact, which are not subject to national surveillance through the NNDSS. These include genital herpes (herpes simplex virus type I and II), genital warts (human papilloma virus, several types), trichomoniasis and parasitic infestations such as pubic lice and scabies.

In addition to the sexually transmissible infections (STI) surveillance by the NNDSS, the Australian Gonococcal Surveillance Programme (AGSP), a national laboratory-based surveillance system, documents the antibiotic sensitivity of gonococcal isolates. The AGSP includes some clinical and demographic data. National data on HIV and AIDS are collected and reported separately by the National Centre in HIV Epidemiology and Clinical Research. The Centre also reports on trends in sexually transmissible infection notifications received via NNDSS. The full report for 1999 is available at www.med.unsw. edu.au/nchecr.

Chancroid

Chancroid is a bacterial infection causing genital ulcers. There have only been 11 cases reported to the NNDSS since 1991. No cases of chancroid were reported in Australia in 1999.

Chlamydial infection

Chlamydial infections were the most commonly reported STI and the third most commonly reported notifiable disease in Australia in 1999, when 14,082 notifications of chlamydial infection were reported to the NNDSS (Table 1). In New South Wales, reporting of genital chlamydial infection commenced in September 1998, so that the reporting for chlamydial infections was national for the first time in 1999. The inclusion of New South Wales data gives a more accurate estimate of the national prevalence than previous years. Chlamydial infections may be under-reported because of a high proportion of asymptomatic infections, particularly among women.²⁹ The recent advent of nucleic acid tests (NAT) for chlamydia may also explain increases in notification; up to 83 per cent (2,747 of 3,298) of chlamydial infections reported to the Laboratory Virology and Serology Reporting Scheme (LabVISE) were detected by nucleic-acid methods.

The majority (92%) of reported cases of chlamydia were in the 15-39 year age range. The notification rate for chlamydial infections in 1999 was 74.2 cases per 100,000 population, higher than the rate of 60.5 cases per 100,000 population reported in 1998.

The male to female ratio was 1:1.5. In both males and females the highest rates of disease were recorded for the 20-24 year age group (Figure 20). High rates of notification were reported from northern Australia, including rates over 400 per 100,000 population in the Northern Territory (Map 5). The National Centre in HIV Epidemiology and Clinical Research (NCHECR) reported rates of chlamydial disease in indigenous Australians from NNDSS data in their annual report. Based on data from the Northern Territory, South Australia and Western Australia, which were the only jurisdictions to report indigenous status in more than half of notifications, the NCHECR estimated a rate of chlamydial infection among indigenous Australians of 882 per 100,000 population compared with a rate of 75 per 100,000 population in non-indigenous Australians.

Figure 20. Notification rate for chlamydial infection, Australia, 1999, by age and sex



Map 5. Chlamydial infection notification rate by Statistical Division of residence, 1999



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Lymphogranuloma venereum

Lymphogranuloma venereum (LGV) is a sexually acquired chlamydial infection caused by certain serovars of Chlamydia trachomatis. The disease begins with a painless genital lesion and may progress to suppurating draining lymph nodes and the development of inguinal buboes. LGV is a common sexually transmitted infection especially in poorer communities in tropical and sub-tropical regions of the world. In Australia, there have only been 7 reports to the NNDSS since 1991 and none since 1995. There were no cases of lymphogranuloma venereum reported from any State or Territory in 1999.

Donovanosis

Donovanosis is a notifiable disease in all jurisdictions except South Australia. Donovanosis is a chronic genital ulcer disease that occurs in indigenous Australians in rural and remote communities. Notifications of donovanosis have fallen significantly over the past 10 years, and particularly since 1994 due to the introduction of more sensitive and acceptable testing methods and more effective treatment with azithromycin. Since 1994, the notification rate of donovanosis has fallen ten-fold from 1.1 per 100,000 population to 0.1 per 100,000 population. Donovanosis only became a notifiable disease in New South Wales in September 1998. A total of 16 notifications were received in 1999, all from the Northern Territory, Queensland or Western Australia. The male to female ratio was 1:7, a ratio consistent with that in 1998. Fifty percent of the notifications were in the 15-29 year age range.

Gonococcal infection

In 1999, a total of 5,676 notifications of gonococcal infection were received nationally (Table 1). The notification rate of 29.9 per 100,000 population continues a steady increase in notifications since 1994 (Figure 21).³⁶ This rate remains far below the very high rates recorded in the 1970s and early 1980s, which peaked at 84.4 per 100,000 population in 1982.³⁷ The number of notifications of gonococcal infection has increased over the past decade. The increase was due in part to an outbreak of gonorrhoea among men who have sex with men in Victoria and to increased testing as part of sexual health programs in Victoria and New South Wales.

Figure 21. Trends in the national notification rate for gonococcal infections, Australia, 1999 to 1999



There was a wide geographical variation in the rate of notification of gonococcal infection (Map 6). The highest rates of notification were from the Northern Territory (590 per 100,000 population) and from northern Statistical Divisions in Western Australia (Map 6). The male to female ratio of 2.2:1 was higher than in previous years. However, the notification rate for females aged 15 to 19 years was higher than for males in the same age group (Figure 22). The NCHECR reported rates of gonococcal disease in indigenous Australians, from NNDSS data in their annual report. Based on data from the Northern Territory, South Australia and Western Australia, which were the only jurisdictions to report indigenous status in more than half of notifications, the NCHECR estimated a rate of gonococcal infection among indigenous Australians at 1,334 per 100,000 population compared with a rate of 17 per 100,000 population in non-indigenous Australians.

Map 6. Gonococcal infections notification rate by Statistical Division of residence, 1999



Figure 22. Notification rate of gonococcal infections, Australia, 1999, by age and sex



A survey of the antibiotic susceptibility of Neisseria gonorrhoeae by the AGSP on 3,740 isolates in 1999 has been published.³⁸ Antibiotic susceptibility patterns varied significantly between regions. Generally rates of resistance to penicillin and quinolone groups of antibiotics were higher in urban than in rural areas.

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Syphilis

A total of 1,979 notifications of syphilis were received in 1999 (Table 1) with a rate of 10.4 per 100,000 population, representing a 16.9 per cent increase in the rate compared with 1998 (1,689 notifications and a rate of 9 per 100,000 population). This increase continues that seen in 1998 and reverses the trends seen since 1992. However, the rate remains lower than those seen in the 1980s. There was wide geographical variation in the notification rate (Table 2, Map 7). While most States and Territories show a slow decline in notification rates for syphilis, Queensland has shown an increase since 1997 (Figure 23). Subsequent information received from the Queensland Communicable Disease Unit suggests that the increase shown is due to poor case definition and the recording of follow-up syphilis serology results on the register. A review of Queensland syphilis registers was undertaken in July 2001. High notification rates continued to be reported from the Northern Territory and Western Australia but these are declining.

Map 7. Syphilis notification rates by Statistical Division of residence, 1999



Figure 23. Notification rate for syphilis, New South Wales, Western Australia and Queensland, 1991 to 1999



The male to female ratio for syphilis notifications was 1.1:1. Notification rates were higher among females than males in age groups younger than 34 years and higher in males than females in age groups older than 35 years (Figure 24). The NCHECR reported rates of syphilis in indigenous Australians based on NNDSS data in their annual report. Based on data from the Northern Territory, South Australia and Western Australia, which were the only jurisdictions to report indigenous status in more than half of notifications, the NCHECR estimated a rate of syphilis among indigenous Australians of 253 per 100,000 population compared with a rate of 3 per 100,000 population in non-indigenous Australians. There were 2 cases of congenital syphilis in 1999, both reported from New South Wales.

Figure 24. Notification rate for syphilis, Australia, 1999, by age and sex




This article was published in Communicable Diseases Intelligence Volume 25, No 4, November 2001.