In this series, we talk to experts to understand various aspects of the current COVID-19 outbreak, the rapid spread of the novel coronavirus and research endeavours in this field. This episode is the first part of a two-part conversation where Shantala Hari Dass (IndiaBioscience, Bangalore) talks to Sitabhra Sinha (Institute of Mathematical Science, Chennai) to understand how to build mathematical models of disease transmission in order to understand the numbers and statistics associated with the current COVID-19 outbreak.