Originally Posted by Gavin@MMW
So... End of season 1 - Scientist guy tells Rick something before he blows up the building..
Now season 2, Walkers are happening without bites..
The virus is either airborne, or too many walkers have gotten in to the water supply.
After the scientest had tested their blood, I *think* what the scientist told Rick is that all of them are already infected - which means that they when they die, they will turn (unless "measures" are taken by the living).
That would explain his seeming lack of surprise when he observed that the security guards were not bitten.