Immunity by Erin Bowman

Survivors of a deadly planetary outbreak take on a new, sinister adversary in the white-knuckle sequel to Contagion.

Thea, Coen, and Nova have escaped from Achlys, only to find themselves imprisoned on a ship they thought was their ticket to safety. Now the nightmare they thought they’d left behind is about to be unleashed as an act of political warfare, putting the entire galaxy at risk.

To prevent an interstellar catastrophe, they’ll have to harness the evil of the deadly Achlys contagion and deploy the only weapons they have left: themselves.