"A pox on thee," goes the old saying. But what if the pox won't cooperate? Collins (What If?
) pursues this ingenious conceit with a sly text and mordantly comic watercolors. Pox, the hero, resembles one of Al Capp's Schmoos and is far too nice to fulfill his destiny as an agent of chickenpox (as opposed to the snarling blue Nurse). When his bunkmates at Germ Academy regale him with tales of how their ancestors induced mumps, tonsilitis, measles and the common cold, Pox responds, "But didn't it make the children miserable?" Ordered to infect a girl named Myrtle—"Mission: Spoil Birthday" read his marching orders—Pox decides to go over to the Immune System side, draws up a plan (a switcheroo involving Myrtle's dog) to defeat a second wave of germs and the child becomes "Mighty Myrtle, The Girl Who Is Never Sick." Collins's imaginative portrayal of the microscopic world involves a giggle-inducing mélange of satire and gross-out humor: the germ for the common cold is a pile of unctuous snot; "Flight School" for germs means leaping off a cliff into facial orifices of a child dummy; the immune system translates into a diminutive white army of Myrtle clones dressed like Joan of Arc. Youngsters will likely deem this book a funny, fitting companion to the cold season. Ages 4-8. (Oct.)