Squirrel tests positive for the bubonic plague in Colorado Symptoms of plague include sudden high fever, chills, headache, and nausea. By Jon Haworth July 14, 2020, 6:34 AM ET 7 min read ABC News Daily: July 14, 2020 Catch up on the developing stories making headlines. Matt Cardy/Getty Images Public health officials have announced that a squirrel in Colorado has tested positive for the bubonic plague. The town of Morrison, Colorado, in Jefferson County, which is just west of Denver, made the startling announcement saying that the squirrel is the first case of plague in the county. “Plague is an infectious disease caused by the bacteria Yersinia pestis, and can be contracted by humans and household animals if proper precautions are not taken,” officials from Jefferson County Public Health (JCPH) said in a statement released to the public.