Project Galileo — Michael Crockett

The second book in the Terra Necro series.
A group of young survivors travel across post apocalypse United States toward Washington State in the hopes of finding sanctuary. But one of them has a secret, a secret that powerful people will do anything to control. Now the young people are traveling across a nightmare world of walking corpses, pursued by two different groups of mercenaries, both of whom will stop at nothing to find them.