There are many normative and technical questions involved in evaluating the quality of software used in epidemiological simulations. In this paper we answer some of these questions and offer practical guidance to practitioners, funders, scientific journals, and consumers of epidemiological research. The heart of our paper is a case study of the Imperial College London (ICL) COVID-19 simulator. We contend that epidemiological simulators should be engineered and evaluated within the framework of safety-critical standards developed by the consensus of the software engineering community for applications such as automotive and aircraft control.