Officials urge that any park visitors who exhibit strange or flu-like symptoms, especially those who stayed in the Curry Village campground, to seek immediate medical attention.
The outbreak has been linked to rodents nesting in the site's popular tent cabins. Humans may contract hantavirus by breathing air exposed to the urine or droppings of infected mice.
Several other cases have been diagnosed and linked to Yosemite. Because of the park's international allure, the World Health Organization and the Department of Health and Human Services have warned more than 30 countries about the outbreak.