The Germ Hunters.

In his camouflage fatigues and mud boots, and with a hunting knife at his hip, Luiz Eloy Pereira looks ready for jungle combat. He is a burly, broad-backed man with rubber gloves over outsize hands. But the enemy today doesn't look like much of a match. "That's him," he announces, peering into an aluminum trap the size of a shoe box. "Bolomys lasiurus." Pereira scoops out his prisoner, a dazed field mouse, and holds it gingerly by the tail. He is standing in a gentle valley where a half-built housing development borders a tuft of woods. This is the interior of So Paulo state, prosperous farm country. But it is also a perfect place for deadly viruses to bloom. "I think ...