By Elise Viebeck - 09/01/12 03:23 PM EDT
Hantavirus presents with vomiting, muscle aches and fever, but brings on more serious effects such as fluid in the lungs, according to the Mayo Clinic. Humans contract the rare sickness by breathing air exposed to the urine or droppings of infected rodents, but the virus does not spread between people.
Yosemite hosts roughly 4 million visitors every year, most of whom stay in and around Curry Village.
The campground's tent cabins have been closed for renovations intended to keep deer mice out. If the effort fails, the cabins may be closed permanently.
An emergency call center related to the outbreak received 900 calls its first day, a Yosemite spokeswoman told the Los Angeles Times.