What is plague?

Plague is an infectious disease caused by a bacterium named Yersinia pestis.

People usually become infected after being bitten by a flea which lives on rats and carries the bug.

What are the symptoms?

The typical sign of the most common form of human plague is a swollen and very tender lymph gland in the neck.

This is known as a bubo - hence the alternative name for the disease of bubonic plague.

Other symptoms include fever, chills, headache, and extreme exhaustion.

Left untreated, the plague bacteria invade the bloodstream and spread throughout the body, causing a severe and often fatal infection.

Infection of the lungs with the plague bacterium causes the pneumonic form of plague, a severe respiratory illness.

Symptoms include high fever, chills, coughing up blood, and breathing difficulty.

How is it treated?

Modern antibiotics such as streptomycin and gentamicin are effective. However, there is concern about growing levels of resistance to the drugs.

People suspected of having the plague should be hospitalised and medically isolated.

It is also important to test people who have been in close contact with sufferers.

What is the risk?

The World Health Organization reports 1,000 to 3,000 cases of plague world-wide every year.

It is found across south Asia, southern Africa and Central America.

Is Black Death the same thing?

For centuries it has been thought that bubonic plague was responsible for a huge wave of disease that swept through Europe in the middle ages, killing approximately one third of the population, and becoming kwown as the Black Death.

However, this assumption has been challenged in recent times, most notably in a book by Samuel Cohn, in which he argues, among other things, that bubonic plague is not deadly enough to trigger the extraordinarily high death rates associated with the Black Death.