Generate an explanation for the given claim using the provided supporting material from the paragraph. Please consider the following points while generating an output. 1) The claim will always have supporting proof in the paragraph, and the paragraph will have a clear point of view supporting the claim. 2) There can be instances where direct correlation to the claim is not available. Make use of the sentences in the paragraph to provide a corresponding output supporting the claim. 3) The explanation should be at least one and at most twelve sentences long.

Paragraph: The National Park Service and the U.S. Public Health Service told the San Francisco Chronicle they launched an investigation after employees and visitors reported the problems this month. Federal officials said they haven't identified the illness or the origin of the outbreak. Park officials said those who had gotten sick are getting better or already recovered. Federal officials were working with Aramark, the concessionaire that operates Yosemite's restaurants, snack shops and hotels, to clean up and disinfect food service facilities in the park, including the famous Ahwahnee Hotel, Yosemite spokesman Scott Gediman said. "The park is reminding all employees and visitors to wash their hands frequently and stay home if they experience any symptoms of a gastrointestinal illness," Gediman said in a statement. A message seeking comment from a spokesman for Aramark has not been returned. Aramark received numerous complaints from visitors about poor food quality, shuttle service and other services since it began managing Yosemite's concessions four years ago. The Ahwahnee Hotel lost its prestigious four-diamond rating by AAA, a distinction the luxury hotel held since 1991, and is now listed as a three-diamond hotel. Visitors to the hotel at the foot of the iconic Half Dome have included Queen Elizabeth II and U.S. presidents. Claim: Stomach illness outbreak at Yosemite prompts major clean-up.
Federal health officials are inspecting Yosemite National Park's food service areas after at least a dozen people have fallen ill with stomach issues.