David Duchovny as Dr. Ira Kane

Julianne Moore as Dr. Allison Reed, CDC

Orlando Jones as Prof. Harry Phineas Block

Seann William Scott as Wayne Grey

Ted Levine as General Russell Woodman

Ty Burrell as Colonel Flemming

Ethan Suplee as Deke

Michael Bower as Danny

Dan Aykroyd as Governor Lewis

Gregory Itzin as Cartwright

Pat Kilbane as Officer Johnson

Sarah Silverman as Denise

Michelle Wolff as Carla

Katharine Towne as Nadine

Stephanie Hodge as Jill Mason

John Cho as Student

Steven Gilborn as Judge Guilder

Wayne Duvall as Dr. Paulson

Kyle Gass as Officer Drake

Jerry Trainor as Tommy

Jennifer Savidge as Clare

Wendy Braun as Nurse Tate

Michael Chapman as Sheriff Long

Mary Pat Gleason as Customer

Andrew Bowen as Road Worker

Chris Wylde as Student

Tom Woodruff Jr. as Lead Primate Creature (uncredited)

Ashley Clark as Lt. Cryer