Some recent visitors to Yosemite National Park have expressed concern that park employees allowed them to be potentially exposed to a deadly rodent-borne disease, even after workers knew previous visitors had contracted the disease.

Eight people are known to have contracted hantavirus pulmonary syndrome between June and mid-August, and three of them died, Yosemite reported last week. The dead include a Kanawha County, W.Va., resident who stayed at Yosemite in June and died within two weeks of the trip.

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