Origin of measles virus: divergence from rinderpest virus between the 11th and 12th centuries.

Measles, caused by measles virus (MeV), is a common infection in children. MeV is a member of the genus Morbillivirus and is most closely related to rinderpest virus (RPV), which is a pathogen of cattle. MeV is thought to have evolved in an environment where cattle and humans lived in close proximity. Understanding the evolutionary history of MeV could answer questions related to divergence times of MeV and RPV. We investigated divergence times using relaxed clock Bayesian phylogenetics. Our estimates reveal that MeV had an evolutionary rate of 6.0-6.5 x 10(-4) substitutions/site/year. It was concluded that the divergence time of the most recent common ancestor of current MeV was the early 20th century. And, divergence between MeV and RPV occurred around the 11th to 12th centuries. The result was unexpected because emergence of MeV was previously considered to have occurred in the prehistoric age. MeV may have originated from virus of non-human species and caused emerging infectious diseases around the 11th to 12th centuries. In such cases, investigating measles would give important information about the course of emerging infectious diseases.