Can You Catch The Plague?

We think of the plague and other medieval diseases as relics from the past. Russell Deeks investigates how scientifically likely you are to catch them.

- Russell Deeks

Ring-a-ring o’ rosies, a pocket full o’ posies. A-tishoo! A-tishoo! We all fall down. For most of us, this deceptively macabre nursery rhyme is the sole legacy of the bubonic plague, a killer disease that once wiped out a quarter of Europe’s population. Bubonic plague has, we tend to assume, been safely relegated to the dustbin of medical history.

Except that’s not true. Europe may have been largely free of the disease since the early 18th Century, but unlike smallpox, it’s never been truly eradicated. Outbreaks of bubonic plague still occur fairly regularly in the developing world, while even in the USA there are seven cases a year, on average. So should we be worried?

Horrible history

Bubonic plague is caused by the bacterium Yersinia pestis. This rod-shaped, anaerobic microbe lives in the guts of fleas, which in turn live on small rodents including rats, gerbils and prairie dogs. Should an infected flea then bite a human being, the bacterium attacks the lymph glands in the armpits and groin, causing the characteristic swellings – buboes – that give the disease its name. Sufferers also experience flu-like symptoms: severe fever, chills, muscle cramps, aching limbs, coughing and difficulty breathing. Gangrene and haematemesis (vomiting blood) can also occur.

If untreated, 60 per cent of victims will die within a few days. If antibiotics are given within 24 hours of symptoms appearing, however, the mortality rate drops to less than 15 per cent.

If the infection spreads to the bloodstream, it is known as septicaemic plague; if it spreads to the lungs, it becomes pneumonic plague. The latter is particularly troublesome because this form of the disease can be spread directly between humans.