A while ago a researcher at the Univ. of Chicago died of the plague. Although most labs use a mutated form that can't get iron needed to reproduce, he had a medical condition that caused an excess of iron in his blood that might have yet the bacteria grow.

However, every year there's a few deaths in the US from the plague because it's present in a variety of animals. If you look worldwide, there's probably on the order of a thousand deaths annually.