This book by Steven Johnson tells how an 1854 cholera epidemic helped lead to the discovery of the way cholera is transmitted and also fired a few more shots in the sorry and old miasma theory of disease transmission. Johnson tells the story well, centering it around a doctor, John Snow. I would be interested to read a biography of John Snow; he's quite the interesting man.
It seemed that there really wasn't enough to the story for a book this long though. A few chapters in a longer book, maybe on finding the sources of various infectious diseases, would have been enough. The subtitle was rather optimistic- The Story of London's Most Terrifying Epidemic -- and How It Changed Science, Cities, and the Modern World. Yes, this particular epidemic may have had an impact on all of those things, but Johnson certainly didn't convince me that it drastically changed anything that wasn't already changing.
Recommended, but if you want to skip that last few chapters, you wouldn't be missing much.