To project the noise correctly onto the center manifold, we will derive a normal form coordinate transform for the complete stochastic system of transformed equations of the SEIR model given by Eqs. ͑20a͒-͑20c͒. The particular method we use to construct the normal form coordinate transform not only reduces the dimension of the dynamics, but also separates all of the fast processes from all of the slow processes. 25 This technique has been modified and applied to the large fluctuations of multiscale problems. 17 Many publications [19] [20] [21] [22] discuss the simplification of a stochastic dynamical system using a stochastic normal form transformation. In some of this work, 19, 22 anticipative noise processes appeared in the normal form transformations, but these integrals of the noise process into the future were not dealt with rigorously.