The number of new COVID-19 cases has been rising in several parts of Canada and health experts are worried. But what do these daily and weekly totals really mean? What's a "reproduction number" and why is it important? Epidemiologist Dr. David Fisman, one of Canada's top experts on the mathematics of infectious disease, joins us on The Dose to explain what these numbers say about how COVID-19 will affect our lives this fall and what we can do to change them.