Hantavirus Infections from Yosemite Continue to be Reported

The number of individuals who have contracted hantavirus infections at Yosemite Park has increased to nine, as the park begins exterminating some of the deer mice believed to carry the virus and expands warnings to include more than 230,000 visitors since early June 2012. 

At least three people have died among the nine confirmed hantavirus infections at Yosemite Park, including seven residents of California, one from Pennsylvania and one from West Virginia.

Hantavirus infections can incubate for up to six weeks until common symptoms appear. Early symptoms include fever, headaches, muscle aches, stomach problems, dizziness and chills, which are often confused with influenza and may go undiagnosed or treated. As a result, the virus has a mortality rate of about 38 percent.

According to reports, the six Yosemite hantavirus infections that have not resulted in death involve individuals who have now recovered and are no longer in danger of life-threatening injury.

Health officials believe the Yosemite Park hantavirus outbreak was started by deer mice, who were able to invest the double-walled Signature tent cabins of Curry Village. A previous report estimated that about 20% of the deer mice in the park carry the Hantavirus.

Hantavirus infections are transferred to humans when they breathe air contaminated with the virus or come in contact with deer mouse saliva, urine or droppings infected with it. The deer mouse is native to the central and western United States and Canada.

Park officials began trapping and killing deer mice in the historic park after determining that rising population levels may have contributed to the recent hantavirus outbreak.

Initial warnings only involved about 2,900 letters sent out earlier this month to individuals who stayed in the Signature Tent Cabins in the Curry Village section of the park. However, the U.S. Centers for Disease Control and Prevention (CDC) subsequently indicated that an estimated 10,000 visitors may have been exposed to hantavirus at Yosemite when accounting for guests who came with the registered visitors who received the warning letters.

Federal health officials later added another 12,000 visitors who stayed at the more remote High Sierra Camps at Yosemite Park, and a new warning issued on September 12 now includes 230,000 overnight visitors to the park since early June.

Photo Courtesy of MiguelVieira via Flickr/CC 2.0