In the summer of 1793, yellow fever swept through Philadelphia, killing thousands of people at a time when the city had no plumbing or sewage facilities. While these filthy conditions did not cause the disease, Maiken Scott, host of WHYY’s The Pulse, explains why the epidemic actually led to cleaning up the city — and to the creation of modern public health.

Maiken and historian Michael Yudell recently created an audio walking tour where you can visit five sites around Philadelphia’s historic Old City to learn about the outbreak. Read more and check out the tour here.