Daily chart: The return of the plague

Main image:  BUBONIC plague brought terror to medieval Europe. Over a third of its population perished from the “Black Death” in the 14th century, hastening the end of the feudal system. As a bacterial disease, the plague these days is generally treatable with modern antibiotics. Nonetheless, it persists beyond the grim chapters of history. On June 26th health authorities in New Mexico, in the south-western United States, announced that three people had been diagnosed with the disease in the previous month alone. This is a marked uptick for a country that records around seven cases a year nationwide, according to the US Centres for Disease Control and Prevention.Zoonotic diseases such as the plague, Ebola and avian flu—which are generally carried by animals—are extremely hard to eradicate. The plague is caused by a bacterium, Yersinia pestis, which infects fleas, which in turn live mainly on rodents. In Europe, those fleas lived mostly on black rats. In America’s south-west, the site of most cases observed in the rich world, the fleas have shifted to rural squirrels and prairie dogs. No vaccine has been developed for the plague, and if the illness is not treated quickly with drugs the death rate is high. The most common form is the bubonic plague, which is spread by flea bites or by contact with ...