Background: In 1997, the World Health Assembly adopted Resolution 50.29, committing to the elimination of lymphatic filariasis (LF) as a public health problem, subsequently targeted for 2020. The initial estimates were that 1.2 billion people were at-risk for LF infection globally. Now, 13 years after the Global Programme to Eliminate Lymphatic Filariasis (GPELF) began implementing mass drug administration (MDA) against LF in 2000-during which over 4.4 billion treatments have been distributed in 56 endemic countries-it is most appropriate to estimate the impact that the MDA has had on reducing the population at risk of LF.

Methodology/principal findings: To assess GPELF progress in reducing the population at-risk for LF, we developed a model based on defining reductions in risk of infection among cohorts of treated populations following each round of MDA. The model estimates that the number of people currently at risk of infection decreased by 46% to 789 million through 2012.

Conclusions/significance: Important progress has been made in the global efforts to eliminate LF, but significant scale-up is required over the next 8 years to reach the 2020 elimination goal.

I have read the journal's policy and the authors of this manuscript have the following competing interests: Mark Bradley is an employee of GlaxoSmithKline. This does not alter our adherence to all PLOS NTDs policies on sharing data and materials.

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