Hantavirus, bubonic plague, and rabies are wildlife-related diseases that occur with some regularity in the southwest. Casual visitors to the park are unlikely to be exposed, but awareness is your best defense. Most important: AVOID CONTACT WITH WILD ANIMALS AND THEIR HOMES.
Hantavirus pulmonary syndrome is a potentially deadly disease spread by infected wild rodents, especially mice. The virus is present in their urine, droppings, saliva, and nesting materials. People become infected when the virus becomes airborne - when dust is stirred up or nests are disturbed, especially in confined spaces. This is one of the reasons that some of the more intact cliff dwelling rooms have been closed. Please respect the signs and protect yourself from possible exposure.
Bubonic plague, the “Black Death” of the Middle Ages, is often present in rodent populations, especially ground squirrels and prairie dogs. It is usually spread by bites from infected fleas. For your protection, do not handle wild animals, either living or dead, and report any dead animals found in the park.
Rabies is a fatal disease spread by the bite of an infected animal. Any warm-blooded animal can get rabies; the most common confirmed cases are in raccoons, skunks, bats, foxes, coyotes, cats and dogs. Do not handle or feed wild animals. Avoid any animal that behaves strangely or seems abnormally friendly, and report it to a ranger. Where dogs are permitted, keep them on a leash to prevent encounters with sick wildlife.
Chances are good that you will never experience any of the above diseases or situations. There is no reason to fear the outdoors or the animals that live there. But awareness and simple precautions can protect you and others from a variety of unpleasant events.