It's a disease most doctors have only seen in text books, the Bubonic Plague.  But some doctors in Colorado were forced to treat it.  That's because a 7 year old girl contracted the disease. 

Doctors suspect the little girl got the disease while on a camping trip.  Her parents say she had been around a dead squirrel.  The disease is transferred mainly through small rodents and their fleas.  Without treatment, the bubonic plague kills about two thirds of infected humans within 4 days.

Bubonic plague is generally believed to be the cause of the Black Death that swept through Europe in the 14th century.  It killed an estimated 25 million people, or 30–60% of the European population.

FactFinder 12 looked into the rareness of the disease.  According to the Centers for Disease Control and Prevention, there is an average of about 7 human cases of the plague each year in the U.S.50% of those cases are in people 12-45 years old.  Since 1900, there have been 999 reported cases of the Bubonic Plague in the U.S.

Click here for a map showing which states have had the most reported cases of the disease.