Biologists at the University of Liverpool have discovered how the plagues of the Middle Ages have made around 10% of Europeans resistant to HIV. Scientists have known for some time that these individuals carry a genetic mutation (known as CCR5-Ä32) that prevents the virus from entering the cells of the immune system but have been unable to account for the high levels of the gene in Scandinavia and relatively low levels in areas bordering the Mediterranean. They have also been puzzled by the fact that HIV emerged only recently and could not have played a role in raising the frequency of the mutation to the high levels found in some Europeans today. Professor Christopher Duncan and Dr Susan Scott from the University’s School of Biological Sciences, whose research is published in the March edition of Journal of Medical Genetics, attribute the frequency of the CCR5-Ä32 mutation to its protection from another deadly viral disease, acting over a sustained period in bygone historic times.
