The term "plague" is a bit of a scary one. Occasionally, Americans ask what I mean by the term "mouse plague" because they don't experience the population explosions we see. I think Australia and China are the only places we see these massive "plagues".
Americans are more familiar with the disease Plague, as they regularly hear of it hosted in some of their wildlife. Worldwide, there are still about 2,000 cases annually claiming 100-200 lives. The Plague of Justinian, the Black Death and the Great Plague each altered the course of history and were each caused by the flea-borne-rat-borne bacteria Yersinia pestis (although this wasn't known until 1884).
Probably 25 million Europeans, or one third of the population, died of the Black Death in 1346/47. Many more probably died in Asia, where it originated. The Mongols besieging the city of Caffa on the Black Sea (in present day Ukraine) were afflicted and had to abandon their siege. But in undoubtedly the worst biological attack in history, they catapulted dead bodies into the besieged city. The fleeing residents of Caffa took the Black Death with them and all of Europe felt the consequences in the next several years.
Interestingly, the displacement of the black, or ship, rat with the brown, or Norway rat reduced subsequent flare-ups of Plague. The brown rat tends to live in sewers rather than directly with people and the less contact with rats, the less contact with rat fleas and therefore the plague bacterium.
The Plague isn't one of the 10 Plagues of Exodus. God's plagues on the Egyptians were blood, frogs, lice, flies, livestock disease, boils, hail, locusts, darkness and the death of the firstborn. The Egyptian's boils were too mild to be Plague. Agonising bulboes, or black lymph nodes in the groin, armpit and neck are the defining feature of Bubonic Plague. That form kills half the people it afflicts. Pnuemonic Plague, caused by inhaling the bacteria from other victims and Septicemic Plague caused by direct infection of the blood kill virtually 100% of those afflicted. All are caused by Yersinia pestis.
Of the Exodus plagues, I think we can claim frogs or toads (surely the easiest one to cope with - although thine ovens and thy kneading bowls were filled) and locusts as modern phenomena in Australia.
Image courtesy of Center for Disease Control.