Sorting Out the Plague
This chapter explores the complex interactions among mammal hosts, insect vectors, bacteria and even amoebae implicated in the movement of the plague around the world. As it shows, trying to find the cause for the three plague pandemics is similar to the way a television detective solves a murder mystery. While the third pandemic established the roles of rats, rat fleas, and bacteria, that explanation has been incorrectly applied to explain the first two pandemics. The chapter shows how bacterial DNA collected from the teeth of 6th-Century plague victims, exhumed 1,400 years later, established greater understanding of the rate and geographic extent of the plague's spread. It goes on to relate how the age-old conclusions that brown rats were disease reservoirs and their fleas were vectors have been reconsidered, assigning rats and fleas specific roles and recognizing that humans and human lice as host and vector are more consistent with the plague’s rapid spread. Using clues from hosts and vectors to solve the mystery requires investigators to be like detectives.