Each fall, millions of hunters across North America make their way into forests and grasslands to kill deer. Over the winter, people chow down on the venison steaks, sausage, and burgers made from the animals.

These hunters, however, are not just on the front lines of an American tradition. Infectious disease researchers say they are also on the front lines of what could be a serious threat to public health: chronic wasting disease.

The neurological disease, which is contagious, rapidly spreading, and always fatal, is caused by misfolded proteins called prions. It currently is known to infect only members of the cervid family — elk, deer, reindeer, caribou, and moose.

Animal disease scientists are alarmed about the rapid spread of CWD in deer. Recent research shows that the barrier to a spillover into humans is less formidable than previously believed and that the prions causing the disease may be evolving to become more able to infect humans.