Background:
Hantavirus was discovered in 1993 in the "Four Corners," an area of the Southwest shared by New Mexico, Arizona, Colorado, and Utah. Initial fatality rates were above 50%, it is down to 33% now. Since then it has been identified in over half of the states of the U.S. and it was determined that it had actually been present, but unrecognized, at least as early as 1959.
Source: CDC Hantaviruses

There have only been 465 cases reported. Most in the west: 73 in NM, 53 in CO, 51 in AZ, 41 in Calif., 35 in WA, 33 in TX, 30 in UT, 21 in NV, ... 1 in NY, 1, MA, 0 in NJ, 0 in MI
Another Yosemite camper dies in hantavirus outbreak - CNN.com - 2012
See: CDC Epidemiology Map

Hantavirus which is spread by rodents can cause several diseases:
Hantavirus pulmonary syndrome (HPS)
and Hemorrhagic fever with renal syndrome (HFRS)

Hantavirus pulmonary syndrome (HPS) is a deadly disease from rodents.

All About Hantaviruses www.cdc.gov/ncidod/diseases/hanta/hps/

Symptoms: www.cdc.gov/ncidod/diseases/hanta/hps/noframes/symptoms.htm

http://www.cdc.gov/ncidod/diseases/hanta/hps/noframes/phys/clinical.htm Clinical Disease Manifestations

Presentation and First Evaluation

Patients with HPS typically present in a very nonspecific way with a relatively short febrile prodrome lasting 3-5 days. In addition to fever and myalgias, early symptoms include headache, chills, dizziness, non-productive cough, nausea, vomiting, and other gastrointestinal symptoms. Malaise, diarrhea, and lightheadedness are reported by approximately half of all patients, with less frequent reports of arthralgias, back pain, and abdominal pain. Patients may report shortness of breath, (respiratory rate usually 26 - 30 times per minute). Typical findings on initial presentation include fever, tachypnea and tachycardia. The physical examination is usually otherwise normal.

HPS Clinical Presentation

The diagnosis is seldom made at this stage, as cough and tachypnea generally do not develop until approximately day seven. Once the cardiopulmonary phase begins, however, the disease progresses rapidly, necessitating hospitalization and often ventilation within 24 hours.

Signs that make a diagnosis of HPS unlikely include rashes, conjunctival or other hemorrhages, throat or conjunctival erythema, petechiae, and peripheral or periorbital edema.

Clinical Assessment

If a hantavirus infection is suspected, a CBC and blood chemistry should be repeated every 8 to 12 hours.

There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.

Due to the small number of HPS cases, the "incubation time" is not positively known. However, on the basis of limited information, it appears that symptoms may develop between 1 and 5 weeks after exposure to urine, droppings, or saliva of infected rodents.

Hemorrhagic fever with renal syndrome (HFRS) is a group of clinically similar illnesses caused by hantaviruses from the family Bunyaviridae. HFRS includes diseases such as Korean hemorrhagic fever, epidemic hemorrhagic fever, and nephropathis epidemica. The viruses that cause HFRS include Hantaan, Dobrava-Belgrade, Seoul, and Puumala.
www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/hfrs.htm

Symptoms of HFRS usually develop within 1 to 2 weeks after exposure to infectious material, but in rare cases, they may take up to 8 weeks to develop. Initial symptoms begin suddenly and include intense headaches, back and abdominal pain, fever, chills, nausea, and blurred vision.

Later symptoms can include low blood pressure, acute shock, vascular leakage, and acute kidney failure, which can cause severe fluid overload. The severity of the disease varies depending upon the virus causing the infection.

• Researchers believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth.
• Researchers also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.
• It is also transmitted thru aerosolization. Aerosolization occurs when dried materials contaminated by rodent excreta or saliva are disturbed. Humans become infected by breathing in these infectious aerosols.

CDC links:
How Do I Prevent HPS?
What you need to know
Prevention at NIH Medline Plus
Prevention Post-It Card Another Yosemite camper dies in hantavirus outbreak - CNN.com - 2012

Sierra Nevada and Nevada State Specifics

Hantavirus Survey Data www.co.washoe.nv.us/health/ehs/vector/hantavirus.html

12-33% of deer mice tested in Washoe Co. NV in 2002-2004 had Hantavirus

A hantavirus caused the death of Elko Co. (Northeastern) NV in June 2006. www.krnv.com/Global/story.asp?S=5081895

Nevada Co., CA Environmental Health Report

Hantavirus has also been detected in the Sierra Nevada region. There have been two major hantavirus incidents in the past two years, involving one human death and one acute hospital stay.

new.mynevadacounty.com/eh/index.cfm?ccs=790&cs=618

Environmental Health Truckee Office: 530-582-7884
Stacie Badgett 530-582-7709 stacie.badgett@co.nevada.ca.us
10075 Levon Ave., Suite 105, Truckee, CA 96161

Links:
CDC Hantaviruses
  What you need to know
  How Do I Prevent HPS? at the CDC.
Hantavirus at NIH: Medline Plus

Hantavirus fact sheet at King's County Wash.