"Virus sickens 200 at Yellowstone, Grand Teton parks" 
News Daily Jun 20 
http://www.newsdaily.com/health/5033138d8fa7948e3bd6a6bc4b90b01f/virus-sickens-200-at-yellowstone-grand-teton-parks 
"The warning advises visitors to the parks in northwestern Wyoming to wash their hands to stem the spread of the virus, which causes a flu-like ailment whose symptoms include stomach pain and vomiting, park officials said."