The epidemiology of tuberculosis in Victoria

To describe the epidemiology of Mycobacterium tuberculosis (MTb) in Victoria, Australia.

We analysed data from the Victorian Mycobacterium Reference Laboratory database and MTb notifications to Health and Community Services Victoria, for the period 1948 to 1992.

The annual number of notified tuberculosis cases peaked at 1143 in 1954 and declined to 266 in 1992. The incidence rate decreased from 47 to 6.2 per 100,000 in the same period. The pattern of tuberculosis has changed significantly over the last two decades, reflecting the high prevalence of MTb in recent immigrants, particularly in those from South-East Asia. Among people born overseas the number of cases increased from 40% of notifications in 1970 to 80% in 1990; they are younger, more likely to be female and to have extrapulmonary disease, than their Australian-born counterparts. Between 1987 and 1991, the mean annual incidence of tuberculosis in people born in Australia and South-East Asia respectively was 1.5 and 47.5 per 100,000. People born in Vietnam, Cambodia and the Philippines had rates between 100 and 400 per 100,000. These rates have remained stable during the last six years. Almost 50% of migrant patients presented within five years, and 30% within two years, of arrival in Australia. The estimated mean annual incidence of MTb in homeless men between 1984 and June 1992 was 80 per 100,000. Resistance to all first-line drugs increased from 10.8% of all isolates in 1981 to 14.7% in 1990. The incidence of multi-drug resistant MTb (MDR-MTb) has been consistently less than 2% of isolates per year in the past 15 years. There were 14 cases of MTb and HIV between 1985 and June 1992. The mean annual incidence of MTb in people with AIDS is 1579 per 100,000 (range, 570-2420 per 100,000), with a relative risk of 236 (95% confidence interval [CI], 134-414). MDR-MTb has not been documented in HIV-infected individuals in Victoria.

Tuberculosis remains an important public health concern. Groups at high risk include people born overseas, the homeless, and people infected with HIV. Physicians caring for AIDS patients should consider the diagnosis of MTb, since its incidence in AIDS patients is so high. Our data suggest possible shortcomings in current methods of screening and prophylactic treatment of migrants and refugees. The rising rate of drug resistance cannot be ignored. We should consider strategies to ensure judicious use of anti-tuberculous drugs by physicians, and optimal patient compliance. These issues are critical to the future of tuberculosis control in Victoria.