A second Arizona county in two weeks has confirmed that fleas in the area tested positive for plague.
The announcement by Navajo County Public Health officials on Friday comes one week after Coconino County officials found prairie dogs in the area to be carrying fleas with the plague.
Plague is an infectious disease infamous for killing millions of Europeans in the Middle Ages.
The fleas in Navajo County were found near the town of Taylor.
Navajo County advises people to watch for sudden die-offs of groups of prairie dogs or rodents, which might be an indicator of the plague.
Officials have notified residents and plan to treat and closely monitor the rodent burrows.