  The critical properties of the stochastic susceptible-exposed-infected model
on a square lattice is studied by numerical simulations and by the use of
scaling relations. In the presence of an infected individual, a susceptible
becomes either infected or exposed. Once infected or exposed, the individual
remains forever in this state. The stationary properties are shown to be the
same as those of isotropic percolation so that the critical behavior puts the
model into the universality class of dynamic percolation.
