The University of Utah scientists used fluorescent pink, blue, green, yellow and orange talcum powder to track wild mice to learn which ones fought or mated with others the most frequently and therefore were most to blame for transmitting the disease.

The study is the first to show the so-called "20-80 rule" applies to a disease directly transmitted among members of a single species of wildlife, the researchers said. The unofficial rule says a small fraction of a population (roughly 20 percent) accounts for most (about 80 percent) of disease transmission.

"If mice were in contact with a powdered mouse, you'd see the colored bite mark on their ear or tail, or color on their genitals," says Denise Dearing, a University of Utah professor of biology and senior author of the study published online in the British journal Proceedings of the Royal Society B.

Putting it in layman's language, study team member Christy Clay explained: "You knew when they got lucky."

The 20-80 rule also may apply to other diseases such as the West Nile virus and in tick-borne encephalitis, Clay noted.

"We are not proposing you exterminate larger mice" although they are most likely to spread hantavirus, Clay said. "But if you could identify places where the animals are older and heavier, then ostensibly you could make a risk map" to show humans living in rural areas where precautions are most necessary, including avoid breathing dust when sweeping up mouse droppings.