Fig 1. Model structure.
A) Hierarchical demographic structure used in the model. Infected individuals are grouped into households, which are grouped into baris, which are grouped into villages that together define the Matlab Region. Map borders were obtained and used with permission from the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr, b) (https: //github.com/InstituteforDiseaseModeling/community-structure-mediates-polio-transmission/tree/main/PopSim/data/shapefiles). B) Household evolution model. Households are represented as pedigree trees and their composition changes as individuals are born and removed either through death or marriage. The model is parameterized by the age- and sex-specific fertility, mortality, marriage of individuals and the rate with which newlywed couples move out after marriage (S1 Text). C) Poliovirus infection model. On infection, infected individuals receive a boost in OPV-equivalent antibody titer and assigned a shedding duration based on their titer prior to infection. Individual antibody titers are dynamic and declines over time. Viral shedding is measured in cell culture infectivity dose 50 (CCID50) units per fecal oral dose and depends on the antibody titer preceding infection and the time since the infection started. Infections shed less virus during the later stages of infection. D) Contact-based transmission. Simulated poliovirus transmission is the result of direct contact with infected individuals. Multiscale transmission is specified using four contact rates (βhousehold, βbari, βvillage, βintervillage) that specify the number of household, bari, village, and non-village members infected individuals contact per day. Homogeneous transmission (mass action) is specified with a single contact rate (βma) can be used to specify the number of individuals infected individuals contact per day, regardless of household and community structure. This results in a heavy bias towards contacting non-village members who are much more numerous than thehousehold, bari, and village contacts of an individual.