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There’s plague in Arizona. Authorities warn of fleas that can infect people and pets.

Plague is treatable with antibiotics if detected early, but the symptoms can be deadly if untreated. (Video: The Washington Post)

Public health officials in two Arizona counties are warning residents about the discovery of plague bacteria, an endemic concern among those who live in the American Southwest but unsettling, nonetheless, given the disease's devastating impact on human history.

Navajo and Coconino counties are adjacent to one another, and in each community the findings are identical: Fleas carrying Yersinia pestis, the bacterium that causes plague, were discovered this month and pose a potentially grave threat to people and their pets, especially cats.

Here, the U.S. Centers for Disease Control and Prevention demonstrates how the plague is transmitted from fleas to pets and people:

Fleas can bite rabbits, prairie dogs and other rodents — and anything that may eat them — and transfer the disease to pets, who in turn can infect humans. Cats who get plague transmit it through their cough. Dogs typically carry the fleas on their fur.

Health officials cautioned county residents and visitors to keep their pets leashed and to avoid touching dead animals. Evidence of a large die-off could indicate plague is present, they say.

Scientists have been testing a plague vaccine for prairie dogs, enticing them to eat it by baiting them with peanut-butter-flavored treats. The approach has proved effective at lowering death rates and reducing outbreaks in animal colonies, according to a U.S. Geological Survey study published in June.

In humans, plague is treatable with antibiotics if detected early, but the symptoms can grow deadly serious very quickly. Whereas bubonic plague is perhaps the best known form, septicemic plague and pneumonic plague are equally serious. The former can cause an infected person's skin and limbs to turn black and die. The latter afflicts the lungs and can lead to respiratory failure.

Today, fatal human cases are rare, averaging just seven a year in the United States dating to the mid-1920s, when the disease swept through Los Angeles, the last significant outbreak in a major U.S. city. Arizona, California, Colorado and New Mexico experience the highest concentration of cases, though since the 1970s, plague has appeared in Nevada, Oregon, Idaho, Wyoming and parts of western Texas.

Globally, about 1,000 to 2,000 cases of plague are reported annually, with most occurring in Africa.

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