SAN FRANCISCO, Sept 12: Yosemite National Park has begun trapping and killing deer mice whose growing numbers may have helped create the conditions that led to a hantavirus outbreak that has infected eight park visitors, killing three, public health officials said on Tuesday. Yosemite officials in recent weeks have warned some 22,000 people who stayed in the park in California over the summer that they may have been exposed to the rodent-borne lung disease, which kills over a third of those infected. (agencies)