In 2007, a wildlife biologist working for the National Park Service at the Grand Canyon discovered one of the collared mountain lions he had been tracking. The animal was dead. Concerned, he removed the lion’s body, took it home and performed a post-mortem examination. Within a week, he was dead, too. The cause of death for both: Yersinia pestis, commonly known as plague.
The deaths, along with dozens of cases since, are a vivid reminder that the disease is alive and well. Y. pestis is a bacterium that lives in the bellies of fleas, which live on rodents, some of which, like rats, live near humans.