Measles, which killed an estimated 142,000 people in 2017, is one of the most infectious human diseases. But when, where, and how it became a human pathogen is still debated. The closest relative of the measles virus is one that causes rinderpest, a disease that affected cattle, deer, buffalo, and other even-toed ungulate species before it was eradicated in 2011. Most researchers believe both viruses had a common ancestor that infected cattle.
Because measles spreads so fast and infection confers lifelong immunity, scientists estimate it needs populations of 250,000 to a half-million people to avoid burning itself out. Historians believe that the largest cities reached that size around the fourth century B.C.E. But when researchers in Japan used available genomes of the measles and rinderpest viruses to build a phylogenetic tree, enabling them to date the branches, they concluded in 2010 that measles didn’t emerge until the 11th or 12th century C.E.
New research based on genetic sequencing of measles found in a pair of century-old lungs suggests the virus existed 1,500 years earlier than previously thought. The sequencing data helped shed light on a much earlier period in measles’ history, leading the research team to conclude that the virus may have entered the human population as early as the fourth century B.C.E., rather than in medieval times.
Read more: Measles may have emerged when large cities rose, 1500 years earlier than thought – by Kai Kupferschmidt, Science