In this study, we develop methods of inference in the case
that discrete-time epidemic data are available on an infectious
disease whose natural history pertains to an SEIR epidemic
model. Likelihood-based inference for the case when
the time interval is equal to the generation period of the disease
(chain-binomial model) has been considered by Bailey
(1975) and O’Neill and Roberts (1999). In the chain-binomial
model it is assumed that the generation period, that is, the
latent and infectious periods taken together, is fixed. Here we
relax this assumption by allowing both the latent and infectious
period to be stochastic and the data to be observed at
time points whose distances may be different from the length
of the generation period. The introduction of probability densities
for the transition of state variables allows us to formulate
a probabilistic discrete-time model that, for a sufficiently
small interval length, provides a good approximation to the
underlying continuous-time process generated by the stochastic
SEIR model. The likelihood function of the data can then
be approximated on the basis of the transition densities.
Depending on what measurements are available, researchers
dealing with infectious disease data are confronted
1170 C _ 2006, The International Biometric Society