The medical world was stunned in the 1990s when mad cow disease vaulted across species to infect people in Great Britain. Now, researchers fear that a similar condition in deer might also be poised to make the leap in the U-S.

Both mad cow disease and chronic wasting disease of deer are caused by prions [pry′ ons], tiny, infectious proteins that cause brain cells to wither and die.

Since the deer disease was discovered in Wisconsin close to a decade ago, scientists have worried that chronic-wasting prions will build up in wild deer herds and their habitat, where they can survive for years to decades. The longer the build-up, the more likely the prions will jump across species to grazing cattle or even to people who eat venison. Researchers are keeping a close eye on the situation.

Let’s hope that these fears turn out to be groundless and stop the madness for cows, deer — and people.