Hantavirus develops from breathing in dust contaminated with rodent droppings, urine or saliva. Early symptoms include fever and muscle aches, chills, headaches, nausea, vomiting, diarrhea, abdominal pain and coughing.State health spokesman Ralph Montano said officials were advising anyone with those symptoms to seek medical attention and let doctors know if they were camping in Yosemite. He said thousands of people visit the park every month, so it would be impossible to track everyone who had set foot in Curry Village.