  In this paper we are concerned with the contact process on the squared
lattice. The contact process intuitively describes the spread of the infectious
disease on a graph, where an infectious vertex becomes healthy at a constant
rate while a healthy vertex is infected at rate proportional to the number of
infectious neighbors. As the dimension of the lattice grows to infinity, we
give a mean field limit for the survival probability of the process conditioned
on the event that only the origin of the lattice is infected at t=0. The binary
contact path process is a main auxiliary tool for our proof.
