Xenocide

In Lusitania, Ender found a world where humans and pequininos and the Hive Queen could all live together; where three very different intelligent species could find common ground at last. But Lusitania also harbors the descolada, a virus that kills all humans it infects, but which the pequininos require in order to become adults. The Startways Congress so fears the effects of the descolada, should it escape from Lusitania, that they have ordered the destruction of the entire planet, and all who live there. The Fleet is on its way and a second xenocide seems inevitable. Until the fleet vanishes.
The task of discovering how the ships disappeared falls to Gloriously Bright, the most brilliant analytical mind in a world of people bred for superintelligence. There is little doubt that she can solve the puzzle; but will she choose life or death for the three races who live on Lusitania?
Xenocide is the third novel in Orson Scott Card's The Ender Saga.