PHOTO: U.S. NATIONAL LIBRARY OF MEDICINE

With tuberculosis – aka consumption – accounting for 10 percent of deaths in the early 20th century, health-care officials turned to expos to combat the contagion. Medical experts disseminated through medical journals the specific exhibiting tools they believed would educate the public on adopting a disease-resistant lifestyle, including postcards (like the one shown here for the 1909 International Tuberculosis Exhibition in Philadelphia), infographics, and life-size "contrast rooms" in which attendees viewed a space with dirty carpets and soiled bedding, then compared it with sanitized versions of those items.