There are two kind of plague: the bubonic and the pneunomic plague. The latter is one of the most deadly diseases and if an infected person is not treated within 24 hours with antibiotics, there is a real chance he or she dies. Not so long time a go there was an Ebola outbreak in western Africa, but the plague is much worse, but the news media doesn't find it that important. Which i can understand, as we live of course in the modern era and the black death was a disease which decimated the European population centuries ago. So it feels like ancient history, but now it's back and we still don't have a cure. Actually it never left, as the disease is carried by animals as well.
In the globalized world of today an deadly infectious disease like the pneunomic plague can spread really rapidly. All it takes is an infected traveler who is able to board an airplane from let's say Madagascar to Mumbai, India. There is a proper chance other passengers get infected too. A few will switch planes at the airport and before the news can break it, there is a global plague outbreak.
sources:
http://www.who.int/mediacentre/factsheets/fs267/en/
https://arstechnica.com/science/2017/10/madagascar-in-panic-amid-raging-double-plague-outbreak-dozens-dead/