ALERT: Mammoth Cave National Park, along with most of the Mississippi and Ohio River Valleys, are areas classified as highly endemic for histoplasmosis according to Centers for Disease Control (CDC). Histoplasmosis is an infection caused by breathing in spores of a fungus often found in bird and bat droppings. Most people with histoplasmosis never develop symptoms and aren't aware they're infected. But for some people — primarily infants and those with compromised immune systems — histoplasmosis can be serious.
For more information go to: http://www.cdc.gov/fungal/