# epydemic: Epidemic simulations on networks in Python¶

## Vision: A common platform for epidemic simulation¶

epydemic aims to provide a common framework for the scalable and efficient simulation of epidemic processes. The current version of epydemic can simulate an SIR epidemic on a network of $$10^5$$ nodes in about 20s, using PyPy on a modern (Intel Core i7@3.8GHz) workstation.

## What are epidemics?¶

Many common processes can be treated as epidemic, where some condition spreads between the nodes of a network. The most familiar example is a transmissible disease such as flu, where un-infected people become infected through contact with infceted people. Mathematically the population of people form a network (or graph), where the nodes represent people and the edges represent possible contacts between them. An epidemic begins when one or more person is initially infected and begins to spread the disease to his neighbours with some probability. Depending on factors such as the way the network is connected, the probability of a contact giving rise to an infection, the rate at which people recover from the illness and so forth, the disease may come to infect none, some, or all of the people.

It turns out that a lot of interesting processes work mathematically like epidemics. As well as diseases, these include the spread of computer viruses, the spread of rumours on social media (or in the real world), the spread of genetic mutations, and even how soils drain.

Simulating epidemic processes is therefore something a lot of people want to do frequently. However, the actual process of setting up and simulating an epidemic is complicated, and this is especially true when we want to do lots of repetitions of experiments to explore how different parameters affect the way an epidemic behaves.

## What is epydemic?¶

epydemic is a pure Python simulation framework for epidemic processes. It aims to provide the common simulation approaches used in the scientific literature, together with a small set of “common epidemics” that can form the basis for experimentation. epydemic is built on top of epyc, an experiment management package that handles running different simulations either on a single machine or in the cloud.

## Features¶

• Compatible with Python 3.6 and later, as well as with PyPy3

• Optimised internal data structures for performance

• Supports both discrete-time synchronous dynamics and continuous-time stochastic dynamics (Gillespie) simulation

• All details of network processes encapsulated in a single class

• Uses networkx for representing disease networks, allowing random networks to be generated easily and real networks to be imported from outside sources

• Support for a generic compartmented model of disease, allowing complex and custom diseases to be described

• Susceptible-Infected-Removed (SIR), Susceptible-Infected-Susceptible (SIS), and Susceptible-Exposed-Infected-Susceptible (SEIR) models built-in, with variations

• Addition-deletion process to model natural birth and death

• Includes a library for working with generating functions, as used in many research papers in network science

• Integrated with epyc’s labs and experiments, including execution in parallel on compute clusters for doing simulations at scale

• Fully compatible with jupyter notebooks and labs

• Annotated with typing type annotations