Abstract
BACKGROUND: The proportion of persons with infectious TB that need to be cured to reduce prevalence is an important but not well characterized target for TB control. METHODS: We compared infectious TB prevalence from countries with two population-based surveys since 2000, accounting for persons receiving curative treatment and those dying or undergoing natural recovery. Annual incidence was estimated as the proportion of prevalence that, when applied to each year over the interval between the two surveys, yielded the observed second survey prevalence. We then determined the relationship between the proportion of people with TB cured and the change in prevalence in each of the years covered by the surveys. RESULTS: Achieving a decline in prevalence required curing at least 20% of those with infectious TB. None of the countries studied reached the 11% annual decline in prevalence required to yield the END TB goal of a 90% decrease in prevalence over 20 years; this would require diagnosing and curing 35-40% of people with prevalent TB each year. CONCLUSIONS: These results provide targets for achieving the goal of a 90% reduction in TB and indicate that active case finding will be required to reach these targets.