# Using the COMOKIT model to study the impact of the morpho-functional organization of cities on the spread of COVID-19

Kevin Chapuis, Patrick Taillandier, Benoit Gaudou, Arthur Brugière, Alexis Drogoul, Alessandro Araldi, Giovanni Fusco

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## To cite this version:

Kevin Chapuis, Patrick Taillandier, Benoit Gaudou, Arthur Brugière, Alexis Drogoul, et al.. Using the COMOKIT model to study the impact of the morpho-functional organization of cities on the spread of COVID-19. 6th International Workshop on Agent-Based Modelling of Urban Systems (ABMUS @ AAMAS 2021), May 2021, Londres, United Kingdom. pp.61-65. hal-03226688

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Submitted on 15 May 2021

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Distributed under a Creative Commons Attribution 4.0 International License
Using the COMOKIT model to study the
impact of the morpho-functional organization of
cities on the spread of COVID-19.

Kevin Chapuis¹[0000-0003-1743-2224], Patrick

Taillandier²,³,⁴[0000-0003-2939-4827], Benoit Gaudou⁵[0000-0002-9005-3004],

Arthur Brugière³,⁴[0000-0001-7220-449X], Alexis Drogoul³,⁴[0000-0002-9685-9199],

Alessandro Araldi⁶[0000-0002-9732-0857], and Giovanni

Fusco⁶[0000-0002-6171-5486]

¹ UMR 228 ESPACE-DEV, IRD, Université de Montpellier, France

² UR 0875 MIAT, INRAE, Université de Toulouse, France

³ UMI 209 UMMISCO, IRD, Sorbonne Université, France

⁴ Thuyloi University, Hanoi, Vietnam

⁵ UMR 5505 IRIT, Université Toulouse 1 Capitole, CNRS, France

⁶ Université Côte d'Azur, CNRS, ESPACE, Nice, France

Contact author: **kevin.chapuis@gmail.com**

**Keywords:** Agent-based simulation · COVID-19 · GAMA platform · morpho-functional city organization.

# 1 Introduction

Are some urban environments more resistant than others to cope with a pandemic such as the one caused by COVID-19? This question is at the heart of many debates because this pandemic reminds us how vulnerable urban populations can be. It invites us to explore how policies could take advantage of the knowledge of local epidemic dynamics in given morpho-functional contexts to become more place-specific.

The problem is that although an impressive amount of data is now available regarding the impact of the pandemic in different geographical contexts, it is almost impossible to determine the relative importance of the spatial context in comparison to, for instance, social, cultural, epidemiological or political factors. A possible approach to disentangle those determinants is to use realistic simulation models in which the impact of different morpho-functional organizations on the effectiveness of public health policies would be evaluated.

Many models have been produced in recent months to respond to the emergency. While many of these models do not allow space to be taken into account, others, and in particular agent-based models [1], allow it and thus enable realistic morpho-functional organizations to be considered. This is the path followed by the COMOKIT<fnref n="7" /> (COVID-19 Modelling Kit) framework [3]: COMOKIT combines sub-models of person-to-person and environmental transmission, a sub-

<footnote n="7">⁷ https://comokit.org</footnote>
model of individual epidemiological status evolution, an agenda-based one-hour
time step sub-model of human mobility, and a policy intervention sub-model.

We propose in this paper to use COMOKIT to study the impact of the
morpho-functional organization of a city on the containment policies that can
be put in place.

## 2 COMOKIT in a nutshell

COMOKIT has initially been developed to respond to the Vietnamese govern-
ment's need for tools capable of assisting in decision-making on intervention pol-
icy choices (containment, mandatory mask wearing, etc.) at the scale of a small
town (about 10,000 inhabitants). However, it has been designed to be modu-
lar, extensible and able to be deployed in different case studies, with different
available input data.

The core entities of the model are the *Individual* agents: they represent in-
terconnected (relatives, friends, colleagues, etc.) individual inhabitants of the
commune with their individual characteristics (age, gender, employment status)
and their epidemiological status. They perform daily activities depending on
their personal agenda. This agenda is a generated set of *Activity* that can be
shared by several individuals (e.g. going to a restaurant with some friends), de-
pending on the age and family status of the Individual agent. *Building* agents are
the atomic spatial entities where the *Individual* agents can perform an *Activity*.
Two special *Building* kinds have been defined as they have an important role in
the simulation: *outside*, that represents everything outside the studied area, and
*Hospital*, where sick individual agents with critical symptoms can be contained
and healed.

A simulation step is set to represent 1 hour and starts by the agent to agent transmission: contagious *Individual* agents infect other susceptible agents in the same building based on a successful contact conditional probability. Then all *Individual* agents update their epidemic status, e.g. going from susceptible to infected. Next, they execute their daily activities depending on authority allowances. Finally, the Authority agent checks its current Policy and apply it, e.g. to test inhabitants.

## 3 COMOKIT Azur

To study the impact of the morpho-functional organization of cities on the spread
of COVID-19, we focus on the case study of the urban area of Nice (France)
which has been hit particularly hard by the pandemic and is considering the use
of place-specific policies. We thus applied the COMOKIT model on 3 subareas
with very different organization [2]:

- *Nice city center:* this is a compact pedestrian-friendly 19th century city, characterized by high urban density in the form of adjoining apartment buildings, finely meshed urban grid, many leisure facilities and small stores. In addition,
this subarea is used by a large population living in other districts of Nice
who come here to do activities (work, shopping, leisure activities, etc.).

- *Nice suburban residential area:* this area lies outside of the city of Nice proper and is characterized by low population density in single-family homes with gardens, and an equally low level of services. Functional specialisation is the hallmark of this area, which also includes some concentrations of car-based commercial buildings. The overwhelming majority of residents work outside of this subarea. Few outsiders come to the subarea to carry out activities.

- *Nice modernist peripheral area:* this subarea is in an intermediate situation: this subarea is densively populated and mainly composed of collective hous- ing, with a low level of service and a majority of inhabitants working outside of the area.

These different morpho-functional organizations beg the question of the favored
patterns of encounter in the context of the COVID pandemic and of the possible
impact of local containment policies.

We initialized the model using French high-quality data sources: the INSEE (French national institute of Statistics) and IGN (French National Institute of Geography) in addition to OSM data. Simulations were executed from January 24 to October 20, 2020, taking into account the epidemiological context of this period. On each area, we tested three scenarios: the absence of an intervention policy (basic scenario), a realistic policy inspired by government action in France and a hypothetical policy of closing urban areas. Each of the three scenarios follows the temporal development of the measures taken in France during the 1st containment between March 17 and May 11, 2020.

50 replications for each area and each policy were carried out to take into
account the stochasticity of the model.

*First results.* Among other contrasting responses to the French lockdown sce-
nario the simulations carried out allow to highlight a cleavage: on the first hand,
suburb area has being relatively protected against the outbreak, while on the
other hand, the two other areas have been hit by a curve up after the release of
the intervention, even sharper for the intermediate area. This might be explained
by the relative openness of the last two areas, where a half and almost one third
of the population of agents come from outside of the studied area. It clearly
supports the observation that lockdown in itself is not able to stop the outbreak
if it is not followed by targeted interventions to fight again the re-introduction
of new cases.

Another aspect to analyse is the differences regarding the epidemic rebound:
it is sharp in the intermediate area, contained in the city center, and smooth
in the last. This may be explained by the structure of activities and functional
aspects of the urban area: in the city center there are a lot of small workplaces
and retails that lead to a relative low and consistent number of daylong contacts
and a large number of small contacts with interchanging agents; in the suburb
there is very few contacts related to activities such as shopping and working
but many prolonged contact with the same agents again and again, like relatives
and friends; finally the intermediate area has a lot of large building that host
workplaces or mall, leading to a large number of prolonged daylong contact
between agent from within and outside the area. This contrasting responses
should be considered when deploying a unified intervention policy and might be
more effective if considered in conjunction with the specificity of the morpho-
functional aspects of urban areas.

4 Conclusion

In this proposal we briefly introduce the COMOKIT framework that makes it
possible to study the outcome of intervention policy over the course of a SARS-
CoV-2 outbreak at the scale of a city. We apply the model on the city of Nice in
the south of France and explore how different areas of the urban zone respond
to interventions. In particular we demonstrate how important is the openness to
outside areas to foresee lockdown style intervention efficiency and how provided
activities and facilities in an area can impact the course of the outbreak after
the release of the intervention.

While COMOKIT used in several context, we still plan to improve its ability
to represent the new challenges to support mitigation strategies to fight against
the pandemic. More precisely we want to make it possible to explore in depth
spatial aspect of NonPharmaceutical Interventions (NPI), for example we want
to add new feature in the framework to easily implement and test policies entailed
by proposition related to the "NoCovid" strategy and the identification of Green
zones with territorial based planing of the interventions.

Acknowledgements.

The work on COMOKIT is funded by the ANRS (project COV15 of the COVID19-Sud Flash 2020 call for project). Large-scale experiments have been made possible thanks to the partnership between IRD and Electricité de France (EDF) to use their supercomputer GAIA.

References

1. Drogoul, A., Taillandier, P., Gaudou, B., Choisy, M., Chapuis, K., Huynh, Q.N., Nguyen, N.D., Philippon, D., Brugière, A., Larmande, P.: Designing social simulation to (seriously) support decision-making: Comokit, an agent-based modelling toolkit to analyse and compare the impacts of public health interventions against covid-19. Review of Artificial Societies and Social Simulation (2020)

2. Fusco, G., Araldi, A.: The nine forms of the french riviera: Classifying urban fabrics from the pedestrian perspective. 24th ISUF International Conference: City and territory in the Globalization Age, Conference Proceedings pp. 1313–1325 (2017)

3. Gaudou, B., Huynh, Q.N., Philippon, D., Brugière, A., Chapuis, K., Taillandier, P., Larmande, P., Drogoul, A.: COMOKIT: A Modeling Kit to Understand, Analyze, and Compare the Impacts of Mitigation Policies Against the COVID-19 Epidemic at the Scale of a City. Frontiers in Public Health 8, 563247–563247 (2020)