SIMULATION OF AN EPIDEMIC MODEL WITH VECTOR TRANSMISSION

We study a lattice model for vector-mediated transmission of a disease in a population consisting of two species, A and B,
which contract the disease from one another. Individuals of species A are sedentary, while those of species B
(the vector) diffuse in space. Examples of such diseases are malaria, dengue fever, and Pierce's disease in vineyards.
There are several ways of interpreting the model: A contact process (CP) on the A population, mediated by B; a diffusive
epidemic process (DEP) on the B population, mediated by A; or a multicomponent epidemic process in which B and A are equally essential.
The model exhibits a phase transition between an absorbing (infection free) phase and an active one as parameters such as
infection rates and vector density are varied. We study the static and dynamic critical behavior of the model using initial
spreading, initial decay, and quasistationary simulations. Although phase transitions to an absorbing state fall generically
in the directed percolation (DP) universality class, this appears not to be the case for the present model. Our preliminary results
clearly exclude DP scaling for the parameter values studied. Compatibility with DEP scaling remains an open question.
Our results raise the possibility of two phase transitions in the epidemic model with vector transmission, as at
the apparent critical point for survival in spreading and quasistationary behavior, the number of infected individuals in spreading
simulations n(t) grows more slowly than a power law.