The California Department of Public Health has issued a warning about hantavirus, which is spread through contact with rodents and their droppings, urine or saliva.
The warning comes after a young Sacramento area man became severely ill when he contracted the disease in Mono County. Most of the 73 California cases since 1993 have been in the Eastern Sierra.
Doctor Vicki Kramer with the CDPH says the disease is hard to distinguish at first.
"Symptoms start with fever, headache and muscle ache and can progress to severe difficulty breathing. In some cases death can occur," says Kramer.
Thirty percent of hantavirus victims in California have died.
Kramer says to prevent contracting hantavirus avoid rodent droppings and nesting in homes, cabins and other buildings. She says don't sweep or vacuum them because that could send virus particles airborne and they could easily be inhaled.
Kramer says surfaces rodents may have contaminated should be wiped with a bleach solution or a commercial disinfectant.