PARASITOLOGY, book three, officially has a title!
There are many books with that title, some of which I highly recommend, but this is the only one by Mira Grant! Coming in Fall 2015, Chimera will conclude the story of Sally Mitchell, who didn't intend to get swept up in a science fiction universe.
Books in this series:
Parasite (hardback 2013, paperback coming this fall)
Symbiont (coming this fall)
Chimera (coming 2015)
It's a trilogy!