How rare are rare diseases?

The answer is: not very.
You’ve probably read in the news by now that a major outbreak of bubonic plague (yes, that bubonic plague) is striking Madagascar. Reaching at least twenty of the island nation’s 114 districts, including the capital city of Antananarivo, this virulent disease has affected over 500 people. This devastating outbreak is unusually large and rapid, and both civilians and doctors are extremely concerned about its implications.