With the coronavirus all over the news right now, you might want to explore the math of contagious diseases with your students. The lesson Rumors and Measles (from the Nonlinear Functions Fast Track GRASP Math Packet) shows how contagious diseases can be modeled with exponential functions. The lesson shows how the transmission rate of a disease, a measure of how contagious it is, is similar to a growth rate in an exponential function. For example, measles is extremely contagious and has a transmission rate of .9 or 90 percent. This means that about 90% of people exposed to the virus who are not vaccinated will be infected. The transmission rate can be used to predict how many people will be infected after x number of days, starting with one patient. However, measles is not very deadly. Only about 0.2% of people who contract the disease die from the illness.