Fleas have been found to carry the plague in at least two Arizona counties, a publication reported.
Fleas carrying the disease were detected most recently in Navajo county, according to a report by ABC News. The first case was first reported a week ago when officials in Coconino County found infected fleas on local prairie dogs.
Navajo county warned residents to be careful while hiking or in areas where there may be dead animals or fleas present, ABC said.
"Navajo County Health Department is urging the public to take precautions to reduce their risk of exposure to this serious disease, which can be present in fleas, rodents, rabbits and predators that feed upon these animals," the Navajo County Health Department said, according to ABCNews. "The disease can be transmitted to humans and other animals by the bite of an infected flea or by direct contact with an infected animal."