A coupled hidden Markov model for disease interactions

TL;DR

This paper introduces a coupled hidden Markov model to analyze interactions among multiple parasite species in hosts, capturing how the presence of one parasite influences the transition probabilities of others over time.

Contribution

The paper develops a novel coupled hidden Markov model framework that accounts for inter-parasite interactions and uses Gibbs sampling for inference in incomplete longitudinal data.

Findings

Evidence of interactions between several parasite pairs.

Detection of an acquired immune response for two parasites.

Model successfully captures complex parasite dynamics.

Abstract

To investigate interactions between parasite species in a host, a population of field voles was studied longitudinally, with presence or absence of six different parasites measured repeatedly. Although trapping sessions were regular, a different set of voles was caught at each session leading to incomplete profiles for all subjects. We use a discrete-time hidden Markov model for each disease with transition probabilities dependent on covariates via a set of logistic regressions. For each disease the hidden states for each of the other diseases at a given time point form part of the covariate set for the Markov transition probabilities from that time point. This allows us to gauge the influence of each parasite species on the transition probabilities for each of the other parasite species. Inference is performed via a Gibbs sampler, which cycles through each of the diseases, first using an adaptive Metropolis-Hastings step to sample from the conditional posterior of the covariate parameters for that particular disease given the hidden states for all other diseases and then sampling from the hidden states for that disease given the parameters. We find evidence for interactions between several pairs of parasites and of an acquired immune response for two of the parasites.