There are currently more than 76 million students in the U.S. enrolled in school, from pre-K to universities. These students may be playing a quick game of tag before the school doors open; exchanging ideas and colored pencils during art class; or arguing about Lizzo’s latest single in the dining hall. But the very things that can make school such a cool place to be are exactly the same things that can make school a dangerous place to be during an epidemic.

Yet there is no definitive consensus among epidemiologists about the benefits and limitations of school closures. To make matters worse, preventing millions of children from accessing necessities such as the food and warmth they receive at school also carries potentially devastating social costs. So it makes sense to ask when, how, and why closing schools became part of the way we respond to infectious disease.

Schools first became a major public health concern with the expansion of public education, during the 19th century. Once that happened, historian Richard A. Meckel says, “It was fairly obvious to anyone who cared to look that going to school often involved contracting a number of communicable diseases.”

The classroom became a new kind of "diagnostic space," Meckel notes. School and public health authorities on both sides of the Atlantic began to devise systems to monitor each student’s immunological state, using index cards, disease registers and maps of infection transmission within and between classrooms. They developed approaches to disease control that weighed the pros and cons of excluding ill pupils, suspending particular classes or closing entire schools.

Fast forward more than 200 years. We now grapple with COVID-19. In response to the pandemic, school closures began in Wuhan, China early in 2020 and the Italian government announced the closure of all schools in early March. As schools and universities throughout the U.S. decide whether, when and how to close amid the COVID-19 outbreak, these historic examples show the important role epidemic surveillance in schools plays in extending public health authority into people's everyday lives — in ways that can go far beyond disease control itself.