When the homeowner described her ant problem as a plague, the exterminator thought she was being a bit melodramatic. After all, a few bugs aren't exactly a huge calamity.
Centuries ago, if you had admitted to a friend that you had the plague, that friend would have hightailed it in the other direction. In the Middle Ages, the plague was a horribly contagious illness that spread like wildfire through Europe, killing millions of people. Thanks to the introduction of better hygiene and antibiotics, plague doesn't describe a killer disease as often these days. Instead, it commonly overstates an annoyance, like an apartment dweller claiming his building is plagued by cockroaches.