America's deer population is under assault from a fatal neurological disease that is similar to mad cow. It's called chronic wasting disease and has been found in 25 states, from New York to Colorado. The biggest fear is that if it is like mad cow, it may become infectious to humans, though there have been no documented cases of that. Researchers say one large herd in Colorado has been cut in half by the disease. States are still searching for answers in how best to stop the spread.