HIV model overview

EMOD is a modeling framework that supports multiple modes of disease transmission. One of these is person-to-person transmission through a network of relationships. In a contact network, there is a specific transmitter and recipient of every transmission event. To organize the network, individuals form one or more relationships that are remembered over time.

Preference for partners is configurable through the model’s input files. Inside the model, the “supply and demand” for types of partners is balanced by a pair formation algorithm (PFA) that, if desired, can dynamically adjust the rates of relationship formation in each demographic category to produce a constant mixing pattern, even with demographic changes in the population. Alternatively, the dynamic adjustments can be turned off to allow mixing patterns to change in response to demographic changes.

STI Overview

The STI model enables person-to-person transmission of disease, which is distinct from the vector- borne, airborne, or waterborne transmission routes also available in EMOD.

The STI contact network enables users to configure up to three relationship types with different durations, gender-specific levels of concurrency, age patterns of formation, and preference functions. Partnership preference can select for partners with similar or different risk behavior, STI infection status, and sociodemographic groupings that can be used represent geographic location, race, socioeconomic status, and other factors. Concurrency and levels of co-infection can also be configured independently for each risk group.

The balance of “supply and demand” of partners is handled using a feed-forward algorithm that dynamically adjusts the rates of relationship formation as the population structure changes. Feed- forward can be disabled during the simulation to allow future patterns of relationship formation to change in response to demographic shifts in the population.