Matrix understanding in Python

[RavCOder]

I thought that every human have to "infect" by zombies because the result is a matrix of all 1

 Input:
  [[0, 1, 1, 0, 1],
   [0, 1, 0, 1, 0],
   [0, 0, 0, 0, 1],
   [0, 1, 0, 0, 0]]
  Output: 2
  Why?
  At the end of the 1st hour, the status of the grid:
  [[1, 1, 1, 1, 1],
   [1, 1, 1, 1, 1],
   [0, 1, 0, 1, 1],
   [1, 1, 1, 0, 1]]

  At the end of the 2nd hour, the status of the grid:
  [[1, 1, 1, 1, 1],
   [1, 1, 1, 1, 1],
   [1, 1, 1, 1, 1],
   [1, 1, 1, 1, 1]]