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.
All of the at-risk visitors had stayed at the "Signature Tent Cabins" in Yosemite's Curry Village from mid-June through the end of August.
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.
There is no specific treatment for the virus, and about one-third of people who contract it will die. Two other people were infected but are expected to survive.
Yosemite officials say they have conducted additional rodent trapping and is increasing rodent-proofing and trapping measures in tent cabins and buildings throughout the park.
Yosemite officials offered these tips to prevent exposure to hantavirus pulmonary syndrome:
- Avoid areas, especially indoors, where wild rodents are likely to have been present.
- Keep food in tightly sealed containers and store away from rodents.
- Keep rodents out of buildings by removing stacked wood, rubbish piles, and discarded junk from around homes and sealing any holes where rodents could enter.
- When cleaning asleeping or living area, open windows to air out the areas for at least two hours before entering.
- Take care not to stir up dust. Wear plastic gloves and spray areas contaminated with rodent droppings and urine with a 10-percent bleach solution or other household disinfectants and wait at least 15 minutes before cleaning the area. Place the waste in double plastic bags, each tightly sealed, and discard in the trash. Wash hands thoroughly afterward.
- Do not touch or handle live rodents and wear gloves when handling dead rodents. Spray dead rodents with a disinfectant and dispose of in the same way as droppings. Wash hands thoroughly after handling dead rodents.
- If there are large numbers of rodents in a home or other buildings, contact a pest control service to remove them.
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.