About half of the deaths in low income countries are not registered or medically certified for causes. To fill these gaps in evidence, nationwide mortality studies using verbal autopsies in a random sample of homes have been adopted with the Million Death Study in India, the Healthy Sierra Leone (HEAL-SL) study and elsewhere. Mortality data are informative to understand infectious disease epidemiology. Professor Prabhat Jha will illustrate the relevance of mortality data using examples of HIV in India, Malaria in India and Africa, and SARS-CoV-2 worldwide. He will also present OpenMortality.org, where some of the key data are freely available.