Stargate Atlantis (2004)

S05E02 The Seed

Dr. Jennifer Keller becomes the unwitting host for a strange alien organism, prompting a frantic quest by the recently revived Dr. Carson Beckett and the Atlantis team for a serum to rescue her from the rapidly developing threat before it can breach Atlantis. At the same time, Richard Woolsey steps in as the new leader of the Atlantis expedition, succeeding Colonel Samantha Carter and officially joining the team.