In December 2000, researches from the National cancer institute in Maryland, USA, analysed DNA Samples from one hundred residents in Eyam. These people were selected based upon the fact that family should be traceable back to the seventeenth century when the village was struck by bubonic plague.
Their results found that there was a greater than average proportion of the villagers carried a genetic mutation referred to as "CCR5-Delta 32" or "Delta 32''. The mutation gives immunity to bubonic plague.
As Eyam is a small village, almost everyone was exposed to the plague. The people who where not carrying the mutation would almost certainly die. Those who survived where carrying the mutation, they would live on too produce children, who in turn, would also be carrying the mutation. 300 years later, the village still has a higher proportion than average of the mutation.
The research sparked enormous interest, not least because it is known that the Delta 32 mutation, if inherited from both parents, gives immunity to HIV / AIDS.