Trends in tuberculosis and the influence of HIV infection in northern Malawi, 1988–2001

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Abstract
Objective: To document the changing incidence and patterns of tuberculosis (TB) in rural Africa and the extent to which they are influenced by HIV. Methods: As part of longstanding epidemiological studies in Karonga District, Malawi, a series of case control studies of TB and HIV were conducted from 1988 onwards. Data from these studies, from a total population survey, and from the Malawi national census have been used to reconstruct the changes in the TB epidemic in the area from 1988 to 2001, examining the role of HIV. Results: The incidence of all confirmed TB, and of new smear-positive TB, in adults increased to peak in the late 1990s but appears to have decreased since. Two-thirds of cases are now HIV positive. The rise in incidence was greatest in the 30–44-year-old age group and was particularly marked for women, leading to a decrease in the male : female ratio for TB incidence from 1.3 to 0.8. The proportion of new smear-positive TB cases attributable to HIV increased from 17% in 1988–1990 to 57% in 2000–2001, but the estimated rate of smear-positive TB in the absence of HIV decreased from 0.78/1000 to 0.45/1000. Conclusions: Without HIV the incidence of smear-positive TB would have fallen in this population. Instead it has risen and is predominantly affecting young adults and women. There is some evidence that the HIV-associated TB epidemic may have passed its peak.