Continuity mistake: When Brad Pitt and his wife say goodbye, her right arm is extended, but a frame later it's bent and holding Pitt's hand. (00:32:25)
Continuity mistake: When the movie starts with the family lying on the bed, Brad Pitt's arms keep changing positions between frames. (00:03:30)
Continuity mistake: After the Mexican family lets Gerry and his family into their apartment, they sit down on the couch. As Gerry leans over and kisses Rachel's head, Karin's hand is over Connie's left shoulder. The angle changes and suddenly Karin's hand vanishes. (00:17:30)
Continuity mistake: In the scene after the plane crash, Brad Pitt is hanging by the waist with his face towards the ground and blood dripping from it. When he looks up, there are blood trails running down his face rather than towards the front of it. The blood trail should be going from the cuts toward the front of his face, not towards his chin. (01:20:45)
Continuity mistake: As Gerry is handing his daughters a plate of pancakes, he says "You mean a stuffed animal puppy? 'Cause that we can do." As he says this, the camera angle changes and suddenly one of the girl's hands can be seen up in the air together almost in a praying position. The camera cuts again and her hands are back down. (00:03:55)
Continuity mistake: As Gerry enters the ship's command centre the first time, when he starts walking across the floor, we see a bearded man in the background, at the stairs against the wall, talking to someone. The camera angle changes, and he is now sorting through papers perhaps 60-70 feet from where he was just standing. (00:30:30)
Continuity mistake: Three times through the movie, we see the command centre on the ship with people running around. Based on several people's movements, it seems that all these scenes were taken at one time, from different angles - too many of the same people moving the same way, carrying the same things.
Continuity mistake: When Brad Pitt is changing the dressing for the female Israeli soldier on the Belarus plane, the man in the seat next to her appears, disappears and re-appears.
Continuity mistake: Lane is in Jerusalem talking with the Mossad officer just as the zombies are about to cross the wall. In all shots from the front, the left side of the Israeli's face is bathed in sunlight while the right side isn't. In shots from the back, the entire right side is now bathed in sunlight. (01:00:00)
Continuity mistake: In the opening scene, the two girls open the door to their parents' room. Karin's pillow is in the shadow. Sunlight suddenly appears on it just as the two girls are about to jump onto the bed a few seconds later. (00:03:25)
Chosen answer: The significance of showing the blood drop on Gerry's tongue and him spitting it out was to back up the theory that the only way to become a zombie is to be bitten by one. After the blood touched his tongue he ran to the edge of the building and waited 12 seconds (the time it takes to become a zombie) before he stepped off the ledge. If he would have started to change he was going to attempt to jump off the roof before causing harm to his family.
Then how does the scientist at the WHO get infected from a blood sample?
You can't turn by ingesting, or getting the blood on you. It has to enter your bloodstream. The scientist cut his hand and got zombie blood into his bloodstream.
He stuck himself with an infected needle or a "sharps" tool coated with infected fluids, which cut him.
Blood tester is encased in glass. Dr. Testing did not pay attention. His hand was in the case while it was mixing. Glass broke, cut him, testing blood mixed with his.