An Economist’s Guide to Epidemiology Models of Infectious Disease

© 2020 American Economic Association. All rights reserved. Around mid-March 2020, as the United States and much of the rest of the world was facing an unprecedented health threat in the form of COVID-19, an abrupt shift in the tone and policies of the United States and United Kingdom occurred. In early March, Prime Minister Boris Johnson said that "we should all basically just go about our normal daily lives." Likewise, on March 11, President Donald Trump reassured the American people that for "[t]he vast majority of Americans, the risk is very, very low." Just five days later, the Trump administration recommended that "all Americans, including the young and healthy, work to engage in schooling from home when possible. Avoid gathering in groups of more than 10 people. Avoid discretionary travel. And avoid eating and drinking at bars, restaurants, and public food courts" (as reported by Keith 2020). The British government likewise markedly changed course, with a series of partial measures preceding a March 23 lockdown order. Although Trump and Johnson had been receiving briefings about COVID-19 for several weeks, the proximate cause of the shift in both countries appears to have been the March 16 release of a headlinegrabbing epidemiological model produced by London's Imperial College, which predicted that there could be as many as 2,200,000 deaths in the United States and 510,000 in the United Kingdom" (as reported by Landler and Castle 2000).