LONDON Several teams of scientists around the world have, for some time, been studying the possibility that a genetic mutation perpetuated by the organism responsible for bubonic plague, or the Black Death, in the Middle Ages - Yersinia pestis - might give people now carrying the mutation increased resistance to the Human Immunodeficiency Virus (HIV) compared to non-carriers. New research has thrown doubt on the micro-organism that was thought to have caused the Black Death, but the link to HIV resistance seems to remain.

Sue Scott and Chris Duncan from the University of Liverpool have suggested that the bacterium Y. pestis — held to be the causative organism for bubonic plague since the 19th century — may not have been responsible for the epidemic after all. In their book, 'Biology of Plagues' ( Cambridge University Press , 2001) they proposed that the culprit was most likely a filovirus, similar to...