Fleas in Arizona have tested positive for the plague and could spread the deadly disease to humans, according to officials. The plague, which famously killed millions of Europeans during the Black Death, is most commonly carried by fleas and rodents. Prairie dog deaths at Picture Canyon in Arizona alerted officials to the possibility of an outbreak. Parasitic insects from the preserve near a water treatment plant in Flagstaff were found to carry the illness. Scroll down for video . Authorities near Flagstaff, Arizona, have found fleas infected with plague after prairie dogs in Picture Canyon began dying (file photos) The plague, which killed millions of Europeans in the 1300s, causes pustules on the skin and is still contracted by 2,000 people a year (file photo) Human cases have developed from close contact with cats who have preyed on infected vermin and  residents in the Southwest have been warned about dangers of the disease while camping. The Southwestern US is similar to the plains of Central Asia where plague began, Professor David Wagner of Northern Arizona University told the Arizona Daily Sun. Plague is still contracted by as many as 2,000 people a year, according to the World Health Organization, though the vast majority of cases are in sub-Saharan Africa and Madagascar. Prairie dogs are particularly susceptible to illness because they live in social burrows, and 90 per cent of the furry creatures' colony can eventually be wiped out if plague infects one member. The disease's rodent host dies, when fleas will look for more blood to drink, including from people. The vast majority of human plague cases reported in the US are in the arid climate of the Southwest, which scientists say is similar to the disease's homeland of Central Asia . The discovery of the disease at Picture Canyon (pictured) has prompted a warning from authorities about the dangers posed by dead rodents . Insecticide has been sprayed in prairie dog burrows in Picture Canyon to halt the plague's spread. Symptoms of pain in humans include fever, chills and muscle pain. At later stages it causes gangrene and a large amount of pustules, or buboes, on the skin. The incubation period could be up to seven days. Modern medications are effective in fighting the plague, also known by its bacterial name Yersinia pestis,  though it can be deadly if left untreated. The last plague epidemic in the United States was in Los Angeles between 1924 and 1925, according to the Centers for Disease Control. Plague originally came to North America via rodents on steamships from Asia. The bacteria Yersinia pestis originally came to North America on steamship rodents from Asia, and the last outbreak was in Los Angeles in 1924 .
Prairie dog deaths at Picture Canyon led to positive tests on fleas . Residents warned about dangers to pets, especially cats . Disease can wipe out 90 per cent of prairie dogs in a colony .