Scientists are currently examining the squirrel to see if it died of the disease or of other causes. Park officials are using insecticides on squirrel burrows to kill off any fleas, which is how the disease spreads from one animal to another. The Twisted Arrow, Broken Blade and Pima Loops of the Table Mountain campgrounds are closed until further notice, although hiking is still permitted.
The plague killed about a third of Europe’s population in the 14th century but is not nearly as active these days. Only four people have contracted the disease in Los Angeles County since 1984. This map from the Center for Disease Control and Prevention shows each case of the plague in the United States since 1970. About 80% were of the bubonic variety and most cases were not fatal, since antibiotic treatment is usually successful. In related news, researchers at the Max Planck Institute in Germany are developing an easy test to detect the plague in its early stages.
As you can see, there are two main clusters. New Mexico gets about half of all the human infections in the U.S. In the 1980s, the worst plague decade, it had slightly more than a hundred cases. Worldwide, most plague cases are in south central Africa and east Asia. People tend to get it while engaged in outdoor activities.