There is no word in the English language with the emotional impact of "plague". It conveys death on a biblical scale, populations in flight and a world frozen in fear. Yet Yersinia pestis, its cause, is a modest bacterium. It may once have ravaged Europe but today it does not figure among the true global killers.

Improved sanitation, better protection of food stores and control of the rodent population are responsible for its demise. The disease is sufficiently rare today that when infection does occur, it has the power to shock.

Fortunately, its bark is worse than its bite. In infected individuals, plague does not pose the deadly threat of rabies, ebola or Marburg disease. A course of antibiotics, as soon as symptoms appear, is enough to see it off.

What the disease has not lost, however, is the power to terrify, the product of a folk memory handed down the generations that seemed the earthly manifestation of God's wrath. Prayer was once our only defence against the scourge. Today, we may thank God we have medicine, too.