Reports that "black death" has swept through an al-Qaeda camp in north
Africa, killing dozens of trainees, are unproven, but the story
highlights how plague has never been wiped out.
One of the "oldest identifiable diseases known to man", according to
the World Health Organization (WHO), plague tends to be associated in
the developed world with the Middle Ages.
The most notorious pandemic, during the 14th Century, wiped out about
a third of the population of Europe.
Caused by the bacterium Yersinia pestis, plague is primarily a disease
of wild rodents that is spread by their fleas. It can be transmitted
to humans by flea bites or contact with animals infected with the