01801nas a2200265   4500000000100000008004100001260001300042653001500055653002600070653002400096653002800120653001500148653003100163653001100194653002300205100001800228700001600246700001800262700001800280245015300298300001100451490000700462520105200469022001401521       2008                            d  c2008 Sep10aAlgorithms10aCommunicable Diseases10aComputer Simulation10aComputing Methodologies10aDemography10aEpidemiologic Measurements10aHumans10aModels, Biological1 aFischer E A J1 aDe Vlas S J1 aRichardus J H1 aHabbema J D F00aMUSIDH, multiple use of simulated demographic histories, a novel method to reduce computation time in microsimulation models of infectious diseases.  a185-900 v913 a<p>Microsimulation of infectious diseases requires simulation of many life histories of interacting individuals. In particular, relatively rare infections such as leprosy need to be studied in very large populations. Computation time increases disproportionally with the size of the simulated population. We present a novel method, MUSIDH, an acronym for multiple use of simulated demographic histories, to reduce computation time. Demographic history refers to the processes of birth, death and all other demographic events that should be unrelated to the natural course of an infection, thus non-fatal infections. MUSIDH attaches a fixed number of infection histories to each demographic history, and these infection histories interact as if being the infection history of separate individuals. With two examples, mumps and leprosy, we show that the method can give a factor 50 reduction in computation time at the cost of a small loss in precision. The largest reductions are obtained for rare infections with complex demographic histories.</p>  a0169-2607