Modeling an epidemic in an imaginary small town.
Burminster is an imaginary small town whose inhabitants experience an outbreak of infectious disease. The people of the town live in houses or apartments, either singly or as couples who may have children at home. The town has several communal institutions: a hospital, a school that admits children of all ages, a nursery for toddlers, a care home for elderly people and a police station. If they do not work in any of these, people work in factories or shops. ‘Factories’ may be manufacturing companies, warehouses, offices or farms; what they have in common is that they employ workers but do not admit visitors; shops, of course, have both workers and visitors. People travel to work together by public transport. After work they may take their children to a playground or spend the evening with other adults at the cinema or theatre or in a pub.
Once the disease has arrived in the community, anyone may come into contact with infected people and themselves become infected. They may be infected directly, by contact with an infected person, or they may be infected indirectly by contact with surfaces in the home, the workplace or the transit system that have been contaminated by infected people.
As the disease continues to spread, the town authorities may decide to take action. They may decide to close the nursery and school, the non-essential workplaces and shops, or the playgrounds and pubs. They may close them all. They may also advise or enforce restrictions on behaviour, such as enforcing social distancing, the wearing of masks and gloves, or frequent hand washing. If these measures turn out to be effective, the authorities may decide to relax them after a while, but they may be resumed if the disease then begins to flare up again.
The epidemic eventually runs its course and dies out once most people have been infected and either succumbed or recovered and become immune. A complete record of all the infections has been made during the epidemic. This includes how, where and when each case occurred, as well as the history and genealogy of the pathogen itself.
If mutation is allowed, the virus can evolve during the epidemic, either to increase virulence and transmissibility, or to evade the immune response triggered by vaccination or recovery from infection, or both. A complete record of the vaccination status of the inhabitants and the evolution of the virus population is kept.
The code and output of the program used in writing this manuscript will be available when it is posted on medRxiv.
They may also be obtained directly from me by email: graham.bell [at] mcgill.ca.
These are two individual based models for investigating complex communities. They are written in Visual Basic 6.0. Each is associated with a Word file that explains the main features of the model. Exe versions of both models are included and will run if you do not have VB installed, but only on a PC.
- Spatial Neural Community Model: A spatially explicit neutral community model
- Uqbar: A foodweb model with the potential of almost indefinite evolution