A number of distinct methodologies to monitor transmissibility of COVID19 are currently being used in different parts of the world. From phylogenetic analyses to population level surveillance of infections, the approaches employed vary in limitations and require different levels of resource allocation, in terms of both laboratory testing capacity and technical expertise. In this talk we’ll set out a description of the methodology we use, that we believe is a robust approach, and has moderately low overhead in terms of test capacity needed to provide input data for the model. The method — based on the renewal equation for cases of infection, back-calculated from death notifications — will be discussed generally and in the setting of Brazil in particular. Estimates will be presented from the model for the COVID19 epidemic in Brazil, in terms of infection attack rates and effective reproduction number Rt. We look forward to discussing how these estimates should be improved in coming days and weeks, through model refinement and through including new sources of data as they become available.