'Although the plague is typically considered a remnant of the Middle Ages, when unsanitary conditions and rodent infestations prevailed amid the squalor of poverty, this rare but deadly disease appears to be spreading through wealthier communities in New Mexico, researchers report.

Why the plague is popping up in affluent neighborhoods isn’t completely clear, the experts added.

“Where human plague cases occur is linked to where people live and how people interact with their environment,” noted lead researcher Anna Schotthoefer, from the Marshfield Clinic Research Foundation in Wisconsin. “These factors may change over time, necessitating periodic reassessments of the factors that put people at risk.”'

Read more: Middle Ages Scourge of Black Death Popping up in Affluent Regions of U.S.