Message passing for epidemiological interventions on networks with loops

Spreading models capture key dynamics on networks, such as cascading failures in economic systems, (mis)information diffusion, and pathogen transmission. Here, we focus on design intervention problems -- for example, designing optimal vaccination rollouts or wastewater surveillance systems -- which can be solved by comparing outcomes under various counterfactuals. A leading approach to computing these outcomes is message passing, which allows for the rapid and direct computation of the marginal probabilities for each node. However, despite its efficiency, classical message passing tends to overestimate outbreak sizes on real-world networks, leading to incorrect predictions and, thus, interventions. Here, we improve these estimates by using the neighborhood message passing (NMP) framework for the epidemiological calculations. We evaluate the quality of the improved algorithm and demonstrate how it can be used to test possible solutions to three intervention design problems: influence maximization, optimal vaccination, and sentinel surveillance.