The bubonic plague is an incredibly lethal disease that has claimed millions of lives over the course of history. Remember the famous Black Death plague that wiped out a third of humanity back in the 1300s? That was bubonic plague. And one Colorado county is officially on high alert after the plague showed up in fleas harvested from local prairie dogs. Colorado health officials have issued a health alert for Boulder County, warning that dogs and cats can potentially pick up the plague or carry infected fleas from one location to another and that infected fleas can spread the infection to humans. Boulder County residents are asked to remain alert for the symptoms of the plague, which include fever, headache, nausea, pain in the lymph nodes, and vomiting. People experiencing symptoms should seek medical care; the bubonic plague can become fatal for infected humans in less than four days. Despite the disease’s severity, Colorado health officials were careful to note that plague has been active in the Boulder County area since 2005 and is unlikely to spread. It’s also worth remembering that the plague is relatively easy to treat with modern antibiotics. Health officials recommend Boulder residents avoid fleas on their pets, do not handle rodents, and treat known rodent sites with flea preventatives or insecticides.