A 15th century woodcut depicts a patient suffering from the bubonic plague. A pandemic of the disease, the Black Death, killed an estimated 50 million people in Europe between 1346 and 1353. Pictures from History/Universal Images Group/Getty Images hide caption
A crowd watches people dressed in rat and flea costumes to illustrate the creatures that spread bubonic plague, which took millions of lives in India in the early 20th century. The photo was taken on Jan. 1, 1910. Hulton Deutsch/Corbis via Getty Images hide caption
Fleas transmit plague — but the pneumonic plague, the type reported from China this week, can spread from person to person as well. Oxford Science Archive/Print Collector/Getty Images hide caption
The bacterium that causes the plague travels around on fleas. This flea illustration is from Robert Hooke's Micrographia, published in London in 1665. Getty Images hide caption
A municipal worker sprays disinfectant during the clean-up of a market in Madagascar's Anosibe district — a measure to fight the outbreak of bubonic plague, which can be spread by a flea bite. RIJASOLO/AFP/Getty Images hide caption
The bacterium that causes the plague travels around on fleas. This flea illustration is from Robert Hooke's Micrographia, published in London in 1665. Getty Images hide caption
La Belle Limonadiere, hand coloured etching (1816). Lemonade was ubiquitous in mid-17th century Paris. Where the limonadiers went, piles of spent lemon peels followed. As rats nibbled on the peels, they killed off plague-infected fleas, Tom Nealon argues in his new book. Courtesy of The British Library Board/The Overlook Press hide caption
This digitally colorized image shows the yellow-colored Yersinia pestis bacteria, the pathogen that causes bubonic plague, on part of a flea's digestive system. National Institute of Allergy and Infectious Diseases via CDC hide caption
Gerbils are harmless... Right? Peter Knight/Flickr hide caption
Rats are a common sight along the streets of Antananarivo, where trash can go weeks, even months, without being collected. Mike Rajaonarison/Xinhua /Landov hide caption
Mary Mallon, known as "Typhoid Mary," was immune to the typhoid she carried. Working as a cook, she spread the disease in New York and ended up quarantined on Brother Island (above) for more than two decades. Bettmann/Corbis hide caption
A 15th-century Bible depicts a couple suffering from the blisters of the bubonic plague. The same bacterium that ravaged medieval Europe as the "black death" occasionally re-emerges. Corbis hide caption
Graduate student Jennifer Klunk of McMaster University examines a tooth used to decode the genome of the ancient plague. Courtesy of McMaster University hide caption
Yoset, a spiritual healer near Arua, Uganda, works with the Centers for Disease Control and Prevention to detect the plague in his village. Courtesy of Mary Hayden hide caption
A copper engraving from 1656 shows a plague doctor in Rome wearing a protective suit and a mask. Artwork by Paul Furst/Wikimedia.org hide caption