A squirrel in Colorado has tested positive for the bubonic plague, the first case in the region, Jefferson County health authorities said in a statement.The bubonic plague is one of the most infamous diseases in history. Caused by the bacteria Yersinia pestis found in fleas on animals, mostly rodents, the disease was responsible for a series of horrific outbreaks throughout the Middle Ages. One of these outbreaks, known as the Black Death, from 1346-1353, wiped out 30%-60% of human life in Europe and killed off a significant number of the global population. The plague is still found worldwide, but has mostly been found in animals. Most human cases have been seen in Africa.However, humans can still catch the disease, either by being bitten by a flea carrying Yersina pestis or by handing an animal infected with the disease.It's symptoms can include high fever, chills, headache, nausea and extreme pain and swelling of lymph nodes, but can result in serious illness or death without treatment, according to the US CDC. Antibiotics are an effective method of treatment.This news comes around a week following a hospital in Inner Mongolia, China, reporting a suspected human case of the bubonic plague, CNBC reported.According to The New York Times, Inner Mongolia had at least four human cases of the plague in 2019. Two of them, however, were the pneumonic plague, which is a deadlier variant.In order to avoid a potential outbreak of the contagious disease, health officials in Jefferson County are encouraging residents to avoid contact with wild animals and to keep their pets from going outside. The authorities specified that cats are especially susceptible to the disease, and will likely die without immediate treatment.