In the fall of 1918, Colorado business owners started campaigns to pressure Denver Mayor W.F.R. Mills to lift restrictions on businesses and public gatherings designed to combat the influenza outbreak. The restrictions were costing them heaps of money, said the business interests, and besides, the virus appeared to have leveled off. Surely, the greatest risk was past. The mayor relented, lifting the public gathering restrictions in time for the Armistice Day celebration. The crowds that thronged downtown Denver that day sparked a surge in new infections, 650 in the next two weeks and 22 deaths in a single day. In 1918, epidemiology was still a rough science, so Mayor Mills, at least had the excuse of not having a good way to predict how the epidemic might play out. University of Wisconsin engineer and infectious disease modeller Oguzhan Alagoz is working hard to make sure that today’s officials have better tools at their disposal to predict the course of the COVID-19 virus, and hopefully, avoid repeating Mayor Mills’ mistake.