An average of seven cases of plague are reported in the United States each year, most frequently in northern Arizona and New Mexico. There is no evidence to suggest the disease is transmitted by undocumented immigrants. No cases of human to human transmission in the United States have been documented since 1924.

The plague is caused by the bacterium Yersinia pestis and is most commonly contracted from fleas. It can then spread through rodent bites or from handling another infected mammal. 

The human cases are most often of the bubonic plague type, a disease widely known for a catastrophic outbreak in Europe during the Middle Ages. 

The plague can be treated with antibiotics if caught in time, but can be dangerous or fatal if left untreated. 

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The Arizona Center for Investigative Reporting partners with Gigafact to produce fact briefs, or quick-response fact checks, about trending claims relating to Arizona.