Exposure

In ramp.xds, exposure is handled as a very general concept.

• Each stratum has its own local daily EIR, \(E_\ell(t)\):

  • The number of infective bites, per patch, is called fqZ

  • Each human population stratum has a vector describing time at risk

  • Each human population stratum has a blood feeding search weight to model heterogeneous biting, including differences in exposure by age;

  • The blood feeding search weight is used to compute availability, and that modifies exposure relative to other strata, all else equal.

  • The blood feeding model computes a matrix, \(\beta,\) that uses availability and time at risk to allocate infectious bites in patches to humans spending time in those patches.

• The local EIR is translated into a force of infection:

  • Each X component model must supply a function describing the fraction of infectous bites that cause an infection, including effects of pre-erythrocytic immunity

  • A local FoI is computed under a model of environmental heterogeneity, which is based on a model for the distribution of the mean in a homogeneous population stratum. For example, most mosquito catch counts data suggest the distribution of bites per person is negative binomial rather than Poisson.

  • The total FoI is the local FoI combined with a travel FoI. The model for travel malaria is set up later.