"Inspections for rodent infestations and appropriate exclusion efforts, particularly for buildings were people sleep, should be enhanced," it said.
The news comes just days after a Pennsylvania visitor became the second person confirmed to have died of hantavirus pulmonary syndrome. Public health officials confirmed that both victims had stayed at the park's Curry Village in Yosemite Valley.
The 2010 report issued by the California Department of Public Health was commissioned by the park service.
"We worked with Yosemite to evaluate risk and make recommendations to reduce the possibility of transmission to people," added said Vicki Kramer, chief of the vector borne disease section of the health department. "That included reducing the number of mice, and excluding them from structures."
Officials with Yosemite National Park and public health officials with the National Park Service did not immediately return calls seeking comment.
The report had been commissioned after two park visitors fell ill after staying in Tuolumne Meadows, about 4,000 feet higher than Yosemite Valley. The report said that 18 percent of mice trapped for testing at various locations around the park were positive for hantavirus.
Hantavirus can be carried in the urine, saliva and feces of infected deer mice. Humans typically contract the disease by breathing in the rodent feces or urine.
Public health workers have sent warnings to more people who visited Yosemite this summer, saying they could have been exposed to the deadly rodent-borne disease. They also handed out warnings to people entering park gates.
Officials sent emails and letters on Wednesday to another 1,000 people who stayed in tent cabins in Curry Village. That was in addition to 1,700 Curry Village guests who had previously been sent such warnings.
Early symptoms of hantavirus include fever and muscle aches, chills, headaches, nausea, vomiting, diarrhea, abdominal pain and coughing. Health officials advised anyone with those symptoms to seek immediate medical attention.
Yosemite National Park has set up a non-emergency phone line for all questions and concerns related to hantavirus in Yosemite at (209) 372-0822. It will be staffed from 9 a.m. to 5 p.m. daily.
The Associated Press contributed to this report.
