It's under their skin. In Ghana, Africa, a family is in agony. Parasites called guinea worms are eating through their bodies. While the family gets treatment, a health-care worker hunts for the source of the worms. Can he find it before others become infected?High-interest topics, real stories, engaging design, and astonishing photos are the building blocks of the XBooks, a new series of books designed to engage and motivate reluctant and enthusiastic readers alike. How can a bite from a pet prairie dog cause a life-threatening illness? Where does the guinea worm, a parasite that lives under human skin, come from? How can a virus that attacks the brain be related to birds dropping dead at the zoo? With topics based in science, these action-packed books will help students unlock the power and pleasure of reading... and always ask for more!