Is plague still a killer?

BBC News | 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 bacterium.

"There are diseases circulating like this in the world's rodents, and in many cases having very little impact on them," says Mike Begon, professor of ecology at the University of Liverpool.

"You could only get rid of plague if you got rid of all the rodents, and you are never going to do that." But Professor Begon adds: "When diseases can jump the species barrier to infect humans they can have a devastating effect."

As well as the medieval pandemic which led to the name "black death", because of victims' blackened skin, there have been two other worldwide outbreaks in the 6th Century and as recently as the second half of the 19th Century.

WHO still reports between 1,000 and 3,000 cases of plague every year; its figures show 182 deaths from the disease in 2003.

The organisation says plague remains endemic - present in a community at all times, but occurring in low frequency - in many countries in Africa, in the former Soviet Union, the Americas - including parts of the US - and Asia.