A squirrel in Colorado has tested positive for the bubonic plague.The squirrel tested positive on July 11 in the town of Morrison, marking the first case of plague in the county this year, according to a news release from the Jefferson County Public Health (JCPH) department.The disease has been around for centuries and is responsible for the deadliest pandemic in human history. An estimated 50 million people in Europe died during the Black Death pandemic of the Middle Ages.