Skip to main content Skip to navigation


Leprosy is an infectious disease with long, variable periods between infection, onset of symptoms and diagnosis. It is caused primarily by infection with Mycobacterium leprae. Leprosy is curable via multi-drug therapy but may result in permanent disability, particularly if treatment (detection) is delayed.

We use freely available data on the annual incidence of leprosy diagnoses alongside information about the incubation period distribution (IPD) and detection delay distribution (DDD) to make inferences about the underlying population of undiagnosed cases.

Our two-stage — taking account of IPD and DDD — model uses back-calculation to reconstruct the annual numbers of new infections, onsets of symptoms and diagnoses from the observed incidences. We are able to allow for differences in diagnostic success in different time periods and include the effect of delayed detection on the incidence of disability.


  • Medley, G.F., Blok, D.J., Crump, R.E., Hollingsworth, T.D., Galvani, A.P., Ndeffo-Mbah, M.L., Porco, T.C., Richardus, J.H. (2018). Policy Lessons From Quantitative Modeling of Leprosy. Clinical Infectious Diseases. 66(Supp.4):S281—S285. doi:10.1093/cid/ciy005
  • Medley, G.F., Crump, R.E., Lockwood, D.N.J. (2017). Interpreting data in policy & control: The case of leprosy. Indian Journal of Medical Research. 145(Jan):1—3. doi:10.4103/ijmr.IJMR_2027_16
  • Blok, D.J., Crump, R.E., Sundaresh, R., Ndeffo-Mbah, M., Galvani, A.P., Porco, T.C., de Vlas, S.J., Medley, G.F., Richardus, J.H. (2017). Forecasting the new case detection rate of leprosy in four states of Brazil: A comparison of modelling approaches. Epidemics. 18:92—100. doi:10.1016/j.epidem.2017.01.005
  • Crump, R.E., Medley, G.F. (2015). Back-calculating the incidence of infection of leprosy in a Bayesian framework. Parasites & Vectors. 8:534. doi:10.1186/s13071-015-1142-5