Volume 23, Number 1—January 2017
Mathematical Modeling of Programmatic Requirements for Yaws Eradication
|Parameter||Parameter estimate||Source of estimate||Comments|
|R0*||1.08–3.32||Derived from published survey data (17)||The average number of new cases occurring from a single index case in a fully susceptible population|
|Monthly probability of progression from primary to secondary disease without treatment||2.78%–5.56%||Derived from expert opinion and previously published models (1,14)
||All untreated persons with primary disease either develop secondary or latent stage disease, and this occurs over a period of 2–6 mo. Untreated persons with latent cases might relapse for a period of >5 y and become actively infectious again.
|Monthly probability of progression from infectious to latent disease without treatment||13.9%–27.8%|
|Monthly probability of relapse from latent
disease to infectious stage without treatment
|Susceptible at baseline||64%||Derived from published survey data (17)
||Data derived from multiple pre–mass drug administration surveys conducted in communities where yaws is endemic
|Primary yaws at baseline||1.5%|
|Secondary yaws at baseline||1.5%|
|Latent yaws at baseline
|Mass treatment parameters|
|Total community treatment coverage†||65%–95%||Expert opinion and published data on coverage achieved in other mass treatment campaigns (18)||Coverage estimates were chosen to reflect the range achieved in real-world mass drug administration programs for other neglected tropical diseases|
|Total targeted treatment coverage of persons with active cases‡||65%–95%|
|Total targeted treatment coverage of persons with latent cases‡||65%–95%|
|No. rounds of total community treatment†||1–3|
|No. rounds of total targeted treatment‡||0–5|
*R0 (basic reproduction number) is the number of new cases arising from a single index case in a fully susceptible population.
†Total community treatment consists of mass drug administration to all residents in a community where yaws is endemic regardless of clinical or serologic evidence of disease.
‡Total targeted treatment consists of active case finding and treatment of newly identified persons with yaws and their contacts.