2012 Hantavirus Outbreak
In August 2012, the National Park Service announced that there were three confirmed cases and one probable case of Hantavirus pulmonary syndrome in visitors who stayed in Signature Tent Cabins in Curry Village. At the time of the initial announcement, two people had died, and about 10,000 people were possibly at risk.
The outbreak of the virus is thought to have been caused by deer mice nesting in the tent insulation. About 14 percent of Yosemite deer mice carry hantavirus. State health experts had told Yosemite about the possibility of hantavirus infection in 2010, but Yosemite declined to warn visitors because, according to park ranger Jana McCabe, there was only one case of hantavirus pulmonary syndrome out of 4 million visitors in 2010, so a warning might generate too much panic or fear.
By mid August 2012, one man had died and a woman had been sickened by hantavirus. The two did not know each other, and they had stayed in different Curry Village tent cabins in mid June. They developed symptoms several weeks later, and hantavirus was identified as the cause by August 14. Park workers cleaned and inspected the tent cabins, and ranger Kari Cobb stated, "Visitors should not be afraid to stay here."
In late August 2012, two more cases were discovered, and all four cases involved stays in the Signature Tent Cabins during June. The Signature Tent Cabins were built after the 2008 rockfall. They are different from the earlier tent cabins because they are double walled with insulation between the walls. After the two new cases surfaced, all 91 Signature Tent Cabins were closed; about 300 single wall tent cabins remain open.
By early September, eight cases had been identified, and three of the eight had died. Seven (including the 3 fatalities) had stayed in the Signature Tent Cabins, and the eighth had been camping in Yosemite's high country. Yosemite decided to send emails to 230,000 people who made reservations. Three park employees with flu-like symptoms tested positive for a different strain of hantavirus that does not cause hantavirus pulmonary syndrome, so Yosemite is considering testing its workers. The outbreak appears due to an unusual increase in the deer mouse population and the design of the Signature Tent Cabin.