Because people are sleeping in the same bed with the undead and playing video games with them, there is more of a chance someone will be bitten and restart the Zombie Apocalypse, especially because multiple people being careless and being bitten by zombies that they sleep in the same bed with will mean multiple patient zeroes at the same time.
As stated, this notion is absurd. We're already shown in the movie that the government is perfectly capable of stopping a zombie apocalypse already-in-progress completely cold, even though they had no forewarning and no idea it was going to happen or could possibly have happened.
So no, one person — even multiple people — getting bitten is not going to "restart the Zombie Apocalypse" unless you assume that literally everyone has gotten so completely, utterly stupid in less than a month or two that they're incapable of doing the exact thing we literally saw them doing on screen.
Fridge Horror:
As stated, this notion is absurd. We're already shown in the movie that the government is perfectly capable of stopping a zombie apocalypse already-in-progress completely cold, even though they had no forewarning and no idea it was going to happen or could possibly have happened.
So no, one person — even multiple people — getting bitten is not going to "restart the Zombie Apocalypse" unless you assume that literally everyone has gotten so completely, utterly stupid in less than a month or two that they're incapable of doing the exact thing we literally saw them doing on screen.