Continuity mistake: The family car's side view mirror gets knocked off by the police motorcycle and falls in the space between Brad Pitt's car and the one in front of it. When Pitt bends to pick it up, it has moved further up the road, next to the back tyre of the car in front. (00:06:35)
Revealing mistake: When the family's car is about to be hit by the ambulance as they try to escape downtown, Gerry is driving and his wife is up, leaning over the passenger seat talking to their daughter. The camera angle changes to a view from behind, and as the ambulance is about to hit, we can see there is nobody in the car and the ambulance driver is wearing a safety helmet. This is viewable in just a few frames. (00:08:00)
Continuity mistake: Segen and Lane are leaving the WHO facility. Just before walking through the gate, Segen's purple hood is up. In the immediate next shot, as she steps outside, her head is bare. (01:52:25)
Continuity mistake: When Gerry reunites with his family in the Nova Scotia Safe Zone, the boy gets into the family hug, with his sweatshirt hood down. The camera angle changes and it is up. (01:55:35)
Continuity mistake: After the motorcycle cop knocks off his car's mirror, Gerry gets out to pick it up but doesn't shut his door fully, leaving it about half open. When the guy in the red car gets out and asks if he is all right, the door is suddenly not open as wide. Then it is back to how wide it was in the next shot. (00:06:30)
Continuity mistake: As Gerry, Segen, and the head of W.H.O. Are walking through the cafeteria of B-Wing, the head of W.H.O. accidentally kicks a can of Mountain Dew which slides across the floor. Just after this, the other W.H.O. Scientists are shown looking at the three in 3 different security monitors. The movements of the three in each monitor is different and does not match up if you look closely. (01:29:30)
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.