Plague ERAP2 Raised Crohn's Risk

The protective genetic mutation near the ERAP2 gene that helped people survive the Black Death is now a risk factor for the autoimmune disease Crohn's disease. In a 2022 study funded by the NIH, researchers analyzed ancient DNA from people who were buried before, during and after the pandemic in London and Denmark. Individuals carrying two copies of the variant were about 40 percent more likely to survive because their immune cells killed Yersinia pestis more effectively. That stronger immune response appears to have carried a lasting cost by increasing susceptibility to autoimmune diseases in modern humans.

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