An investigation into the deadly hantavirus outbreak in Yosemite National Park last year has concluded that the park's staff acted appropriately in responding and managing the matter.

Ten park visitors were infected by the rodent-carried disease, which produces flu-like symptoms and can lead to fatal respiratory complications, and three died from it. Nationally, the death rate from hantavirus is 38 percent, according to the Centers for Disease Control and Prevention.

Park and concession officials reached out to tens of thousands of visitors who stayed in the park from early June through late August, including some who came from overseas, to alert them to the outbreak and to urge them to seek medical attention if they come down with any of the flu-like symptoms the disease spawns.

A report by the Interior Department's Inspector General's Office stated that the Yosemite staff acted appropriately in responding to the spread of the deadly disease.

According to the report, nine of the visitors contracted the disease while staying in the "Signature" tent cabins managed and rented by Delaware North Parks & Resorts to guests in Curry Village in Yosemite Valley. The 10th possibly contracted the disease in a tent cabin in the park's Tuolumne Meadows lodging area or in one of the park's High Sierra tent camps.

In North America, hantavirus is carried by deer mice and can be found throughout most of the country. In California, about 14 percent of the deer mice in the High Sierra carry the disease, according to National Park Service staff.

In an interview with the Traveler last year, Dr. Danielle Buttke, an epidemiologist for the National Park Service who investigated the outbreak, said the most common way for the disease to spread from a rodent to a human "is to have a mouse urinate in an area, and if it is an infected mouse the virus is spread in the urine and then that urine can be stirred up in dust, and a person would inhale that virus in the dust that’s stirred up. That’s the most common route of infection."

The outbreak led to the discovery of deer mice nesting within the double-walled Signature Tent Cabins. It would, in theory, be possible for urine-contaminated dust from those nests to migrate into the cabin's interior, she said.

In its report (attached), the Inspector General's Office concluded that when the hantavirus outbreak was initially identified, the park staff properly responded “to contain, remediate, and prevent further outbreaks.”

“Specific to policy, we found that the NPS acted according to NPS and Departmental criteria for review and approval of concessionaire plans and proposals, pest monitoring and management activities, inspection of visitor accommodations operated by the concessionaire, as well as information dissemination of hantavirus and other vector-borne diseases,” the report stated.

Going forward, the inspector general's office made the following recommendations for the Park Service to follow:

1. Require NPS health, safety, and building officials to review proposals of new visitor accommodations and modifications to their structures for vector-borne disease vulnerabilities and document the outcome of the reviews before NPS authorizes work on structures;

2. Require NPS health, safety, and building officials to inspect visitor accommodations on a cyclical basis to assess vector-borne disease vulnerabilities.

Specific to NPS oversight of concessions of Yosemite tent cabins, we recommend that the NPS Director:

3. Require DNC to report the results of its monitoring of concession areas to Yosemite health and safety officials; and

4. Require that educational material is made available to all overnight visitor regardless of where they stay.