Dr. Frederick Skvara via Getty Images

Turns out, the plague isn’t just ancient history. New Mexico health officials recently confirmed the first human case of bubonic plague — previously known as the “Black Death” — to surface in the U.S. in 2011.

An unidentified 58-year-old man was hospitalized for a week after suffering from a high fever, pain in his abdomen and groin, and swollen lymph nodes, reports the New York Daily News. (Officials declined to say when the man was released from the hospital.) A blood sample from the man tested positive for the disease.

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Santa Fe officials said they are still investigating how the man contracted plague. Flea bites are the most common method of transmission to humans; in this case, doctors suspect a flea bit the man on his left leg.

Bubonic plague tends to create panic in areas where it appears. That’s understandable, given that it’s best known for having wiped out more than a third of the medieval population of Europe. Today, some 1,000 to 3,000 cases arise globally each year. Countries such as Australia and Europe are plague-free, but regions in Africa, Asia and the Americas have experienced epidemics in recent decades. Most cases occur in small towns and villages or agricultural areas, rather than in developed towns and cities.

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In the U.S., plague cases are rare and relatively isolated; 10 to 20 human cases of plague are reported each year, according to the Centers for Disease Control and Prevention. They typically appear in two general areas: one region includes northern New Mexico, northern Arizona and southern Colorado; the other spans California, southern Oregon and far western Nevada.

Of those states, New Mexico has the highest domestic plague incidence with 65 of the 134 cases reported in the U.S. since 1990, according to a health department report.

Plague is caused by the bacterium Yersinia pestis, which lives in rodents, and is transmitted by flea bites. The Los Angeles Times‘ Booster Shots blog reports:

The fleas feed on wild rodents, such as the rock squirrel in the Southwest and the California ground squirrel in the Pacific states. Prairie dogs, wood rats, chipmunks and, less commonly, rabbits have also been known to carry infected fleas. Cats and, less often, dogs can transmit the plague to humans as well — by carrying fleas into the house or by contracting the plague themselves (through flea bites or by eating plague-infested rodents) and then biting or scratching humans. Very rarely, a cat can develop plague pneumonia and spread the disease by coughing.

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Onset of plague usually occurs two to six days after exposure. Symptoms include fever and headache, followed by pain and swelling in the lymph nodes. About 1 in 7 cases is fatal, but the disease can be treated with antibiotics.