Abstract

The Theory of urban endemo-epidemiogenesis is a general explanatory hypothesis of the processes of emergence and geographic spread of infectious diseases in the city. According to this theory, each city has an urban geosystem of endemo-epidemies structured in two hemispheres, which are in constant opposition or confrontation. The first one is the precursor-hemisphere that is composed to four specific systems: (1) the pathogen, (2) vulnerability, (3) classic itineraries of dissemination and (4) channels of dissemination systems. The second one is the resilient-hemisphere that is also composed to four specific systems: (1) the preventive, (2) health-promoting, (3) curative/healing and (4) surveillance systems. Endemo-epidemiogenesis is a foreseeable and predictable mathematical response to spatialized and temporalized relationships of mistrust or power that are constantly constructed, deconstructed and reconstructed between these two hemispheres from the laws of causality that are identified in this study. The city now becomes a heterogeneous, dynamic and complex socio-spatial order of endemo-epidemiogenesis, unlike the countryside which is a relatively homogeneous, fixed and simplex socio-spatial order of endemo-epidemiogenesis.

1. Introduction

Urbanity is, in essence, an incubator of human well-being, a motor for the production of wealth and human development by generalization. The strong socio-demographic attractiveness of cities makes urbanization a relevant factor in reconfiguring the geographical distribution of the world's population. The urban population, which was less than 10% of the world population at the end of the 19th century, increased to 53% in 2012 and 55% in 2021; it is projected at 68% by 2050 ^{1, 2, 3, 4}. As Rabier and Lamara ⁵ pointed out, by 2030 the world will have 43 “megacities” with more than 10 million inhabitants, compared to 31 now. Modern times have thus conceived a new order of socio-spatial technostructures, namely, “city-states”, as the ancient city-states of antiquity. Cities have become real socio-demographic frameworks in perpetual over-densification.

The management of these socio-spatial technostructures, and above all, the satisfaction of their socio-demographic frameworks with increasingly growing and constantly diversifying needs, constitute the main urban challenges of the 21st century. Urban demand is far greater than supply in terms of housing, nutrition, health care, security, education, job offers, reception infrastructures, social amenities, sanitation, hygiene and safety, waste treatment, depollution, etc. This reality is a precursor to the emergence of a matrix of complex, intertwined and constantly changing impacts. One of the most plausible impacts is the endemo-epidemic crisis. If the status of developer attributed to the city is undeniable ⁶, it is compromised by the prevalence of endemo-epidemies in perpetual mutation and readjustment ^{7, 8, 9}.

Endemo-epidemies refer to a form of pathologies comprising of three dimensions: typology, space and time. According to the first dimension (typology), an endemo-epidemy is an infectious disease type, that is, a disease caused by an infectious or pathogenic microorganism ^{10, 11}. These are germs whose toxic activity is harmful to human health. There are four types of pathogens giving rise to four types of infectious diseases: viruses causing virus infections; bacteria causing bacteriosis; parasites causing parasitosis; fungi causing mycoses ¹². Infection is the process of transmission of this germ to humans by various vectors in the living environment. According to the second dimension (space), endemo-epidemies are infectious diseases that occur in a given locality. They are therefore not to be confused with pandemics which are on a global scale. According to the third dimension (time), it is an infectious disease that rages permanently with epidemiological outbreaks periodically or episodically in a locality where the living environment offers favorable conditions ¹⁰.

In general, the perpetual growth of the epidemiological and socioeconomic effects of urban endemo-epidemies make it a relevant field of research that cuts across multiple development issues ^{13, 14, 15, 16}. This situation is dependent on several factors, including the lack of control over the complexity of the processes of emergence and propagation of the said diseases. This lack of control is the precursor problem of this research. The objective here is to formulate a general explanatory hypothesis contributing to the understanding and mastery of said complexity. It is therefore a question of developing a theory of urban endemo-epidemiogenesis based on the standardization of a set of generalizable causal relationships as proposed by Gnassounou ¹⁷ and Willett ¹⁸, and governing the socio- spatial dynamics of endemo-epidemies in the city. The restitution of this study focuses on three main points: the interpretation of the geosystem of endemo-epidemiogenesis, the reconstitution of the scientific laws of operation of this geosystem and the actual formulation of the Theory.

2. The Geosystem of Urban Endemo-Epidemiogenesis

The geosystem is a concept originating from the Soviet school in the 19th century which experienced an outstanding evolution and better promotion by French geographers from the end of the 1960s ¹⁹. This concept is an intellectual construction of relating different systems in a geographical space; a representation of cause-and-effect interactions between ecological and societal components in an environment; a systematization of the patterns of interrelation between biotic, abiotic and social systems in an environment; a standardization of the dynamics of interaction, inter-influence and interdependence between living systems and their living environment or their environment, the potential balance of which is maintained by the laws of causality... ^{20, 21}. The specification and characterization of a given geosystem is therefore relative to the causal object.

Endemo-epidemies constitute the object of causality in this research. These are infectious diseases determined by a living environment that provides the pathogenic germs that are at their origin. These diseases therefore result from the nature of the cause-and-effect relationships between human society and its living environment ^{22, 23}. The geosystem of endemo-epidemiogenesis therefore refers to a systematized representation of environment-society interactions that are precursors of infectious diseases. It identifies the framework of fertile interference of a set of natural and anthropic systems governed by the relations of cause and effect generating the emergence and the spread of infectious diseases; the product of the structural and functional articulation of eco-pathogenic and socio-pathogenic complexes under the effect of causality in a precise space, etc. This articulation therefore integrates the particularities of space by fertilizing spatially differentiable geo-systems. Urban space, for example, does not always offer the same ecological and societal conditions for the emergence and spread of infectious diseases.

In fact, the heterogeneity and simplicity of the rural living environment predisposes to a homogeneous and simplex endemo-epidemiogenesis geo-system ²⁴. This predisposition is contrasted in urban areas marked by heterogeneity and complexity of the living environment. The contemporary city, due to the multitude of crises it experiences (ecological, demographic, planning, governance, public health, etc.), precisely constitutes a prototype of a living environment predisposing to a geosystem of heterogeneous and complex endemo-epidemiogenesis. A systematized representation of the latter shows two hemispheres, each with a profile of structural or organic systems. First, there is the precursor hemisphere and the resilient hemisphere.

The precursor hemisphere of the urban endemo-epidemiogenesis geosystem refers to all the systems at the origin or favorable to the development of pathogenic germs, the conversion of the pathogen into pathology and the geographical spread of the infectious disease. This hemisphere includes four precursor systems. These are pathogen systems, vulnerability, classic itineraries of dissemination and channels/means of dissemination. Each system operates or operates within an appropriate socio-spatial framework.

- The pathogenic system and the detonating socio-spatial framework of endemo-epidemiogenesis

The pathogenic system refers to all the dispositive, processes, mechanisms and interactions of an ecological and societal order, favoring the development of pathogenic agents. On the one hand, two orders emerge that are articulated in the urban space: ecological and societal. These orders refer to what Sorre ²⁵ outlined as the eco-pathogenic complex (in relation to the natural environment) and the socio-pathogenic complex (in relation to risky human behaviors and practices) respectively. The pathogenic system can therefore be reconsidered as the structural and functional articulation of the eco-pathogenic and socio-pathogenic complexes ^{26, 27, 28}. On the other hand, this system operates in a specific living environment (biotope) and functions with the help of the mediation of living beings (biocenosis). The whole formed by biotope and biocenosis gives rise to an ecosystem. The city constitutes a complex ecosystem where the zoocenosis coexists and intertwines with human society ²⁹. It is therefore a socio-spatial framework favorable to the development of pathogenic germs and the emergence of what Ménard ¹² describes as anthropo-zoonotic diseases.

The urban ecosystem therefore constitutes a socio-spatial framework that triggers endemo-epidemiogenesis from a set of germ foci disseminated in the densely anthropized space ^{8, 22, 30}. These are intermittent sources or reservoirs of germs that are precursors to diffusion processes by transmission and contamination. Some of these hotbeds are; the habitats of germs in cities; that is to say, environments where they find suitable conditions to reproduce and develop. These potentially pathogenic environments can be structured into four classes: natural spaces, anthropized spaces, material support spaces, subject-reservoirs (animals or human beings). A process of endemo-epidemiogenesis can involve some or all the classes of the detonating socio-spatial framework. Each class can be broken down into categories of pathogenic environments depending on the disease. The realities can therefore vary from one pathology to another. However, the establishment of this framework precedes epidemization. On the one hand, the total absence of a germ system of a given pathology in a community explains the total absence of this disease in said community. On the other hand, the insufficiency of the conditions of convertibility of the pathogen into pathology accounts for the presence of a system of specific germs (pathogen) within a community without however recording cases of disease (pathology). In the case of a successful conversion of contagious diseases, the unhealthy subject becomes a new reservoir or subject-reservoir of germs.

-The vulnerability system and the socio-spatial framework of convertibility of the pathogen into pathology

The vulnerability system refers to all the material exposed and vulnerable to invasion by the pathogenic system. It is made up of human beings, animals, plants and the socio-spatial frameworks of convertibility of the pathogen into pathology. Concretely, these settings are, urban sites of contact between germs and healthy subjects; specific places in the city where the transmission of germs to healthy subjects or the contamination of the latter by pathogens takes place ^{31, 32}. These frameworks can be structured into four classes: natural spaces, domestic or private social spaces, public social spaces, socio-professional spaces. A process of endemo-epidemiogenesis can involve some or all the classes of the socio-spatial framework of convertibility of the pathogen into pathology. Each class can be broken down into categories of convertibility media depending on the disease. This process can therefore vary from one pathology to another.

The transfer of germs is the trigger for the conversion of the pathogen into pathology. This is so because it is followed by the invasion and incubation of germs in the individual. Then comes the interactions between the pathological harmfulness of said germs and the immune system of the individual, the alterability and alteration of said system by this harmfulness, and finally, the occurrence of the state of sickness. This last state reflects the end of the conversion process, the duration can range from a few seconds to days, months, or even years depending on the disease. The conversion is therefore processual and depends on several convertibility conditions starting with the presence of the pathogenic system in the community, and therefore, of the detonating framework. These two frameworks may overlap in certain cases. The site serving as a focus of germs is also a place of contact with healthy subjects or a socio-spatial framework of convertibility.

-The system of classic itineraries or routes for the spread of germs

The system of classic itineraries or routes of dissemination of germs represents all the mobility trajectories of pathogenic agents between the socio-spatial frameworks of detonator (dissemination centers) and convertibility (space of contact, transmission, contamination or infection) ^{12, 29, 33}. This mobility takes place during the interactions between the structuring elements of these frameworks. In fact, urban dynamics are governed by an intense continual mobility of people, animals, plants, goods and waste of all kinds. These dynamics offer as many opportunities for moving the germs of endemo-epidemies from one class of the socio-spatial framework to another according to three logics. The first is the detonator intra-frame logic (internal/between the detonator foci). It is governed by a profile of 16 classic travel routes for germs from one class of detonating focus to another (Table 1). The second is the intra-frame logic of convertibility (internal/between spaces of contact, transmission or contamination). It is observed in the case where the space acting as a detonating focus is also a space of contact between germs and healthy individuals. It leads to a profile of 16 classic travel routes of germs from one class of contact space to another (Table 2). The third is the inter-frame logic (between the detonating foci and the contact spaces). It also gives rise to a profile of 16 classic germ mobility routes from a class of detonator focus to a class of convertibility framework (Table 3).

In total, the urban endemo-epidemiogenesis geosystem is governed by a matrix of 48 types of classic germ geographic mobility itineraries or routes. This matrix concerns all urban endemo-epidemies. The grouping by socio-spatial affinity of these trajectories gives rise to three relational instances of classic itineraries. The ecological instance concerns the itineraries relating to Environment-Environment relations. Here, germs move within a frame of natural space or between natural frameworks. This instance is a precursor to the multiplication of natural sources of germs. The societal instance concerns the itineraries relating to Society-Society relations. Germs move within a societal framework without involving the elements of the natural environment, or from such a framework to ours of the same nature. These routes are generally responsible for human-to-human or object-to-object contamination. Some contaminated support can also contaminate other healthy support, thus creating new germ media. Finally, the third and last is the eco-societal instance which concerns the Environment-Society routes at the origin of most of the transmission and contamination of healthy subjects, then of the multiplication of germ outbreaks.

- The channels system of germs diffusion

The channels system of germs diffusion or dissemination refers to the set of vehicles of germs in their geographical mobility within the urban space; it refers to the means and mechanisms for the deportation of germs from detonating foci for the frameworks of convertibility in pathology ³⁴. These channels/means are therefore at the origin of the transmission and contamination of both healthy individuals and healthy spaces by transforming them into detonating foci. As a connecting belt, they play a decisive role in the chains of urban endemo-epidemicity. In their absence, the circuits of endemo-epidemiogenesis and epidemization are broken. There are four main channels operating across all circuits.

Firstly, these are vector-organisms which are harmful organisms involved in the transmission of zoonoses or diseases of animal origin. These vectors-organisms transmit viruses, bacteria or parasites to humans that cause various infectious diseases (malaria, Chikungunya virus fever, Zika virus fever, trypanosomiasis, yellow fever, madness, West Nile virus, Japanese encephalitis, tick-borne encephalitis, etc.). Consumption is the second means of spreading infectious diseases. The consumption of contaminated water, infected food, beathing of polluted air, etc. is a motor for the invasion of various germs (bacteria, viruses, parasites, fungi) into the human body, causing various diseases with endemic-epidemiological potential, such as gastroenteritis (typhoid, dysentery, cholera, amoebiasis, ascariasis, giardiasis, etc.), infections linked to air pollution (influenza, tuberculosis, etc. ). The vector-materials or Handling contaminated materials and substances is the third means of spreading germs. The use of infected objects, the use of contaminated water, etc. creates contact between the reservoirs and healthy subjects. Germs usually settle and contaminate contact points such as hands, skin, mouth… eventually triggering an invasion of germs. Eating without washing the hands, washing plates, vegetables/fruits or bathing with unsafe water (water from the well, stream, and rain, etc.), the use of dirty syringes and blades, handling without protection of substances with bacteriological, viral or chemical toxicity, etc. These are some of the examples of risk behaviors in favor of this invasion participating in the conversion of the pathogen into pathology in said subject. The fourth and last means of transmission is the transfutation considered as a mechanism for the dissemination of germs in a situation of transfusion or defector that may be linked to neo-fetality (from the mother to the fetus), post-fetality or lactation (from the mother to the child), then blood transfusion. The geographical mobility of germs through the 48 types of classic itineraries takes place thanks to these four channels/means. They intervene according to the specificities of each endemo-epidemic.

The resilient-hemisphere refers to all the systems and provisions, strategies and practices for combating urban endemo-epidemies. It is composed of the four systems: preventive, promotional, curative and endemo-epidemiological surveillance. These systems are better developed in the city in accordance with the strong urban demand imposing a geopolitics of metropolisation of the public health offer ³⁵.

- The prevention system

The prevention system refers to the measures and provisions that systematically prevent the geographical appearance and spread of infectious diseases. It is implemented by all categories of urban actors in the context of community health ^{36, 37}. It is structured into two paradigms. First, there is environmental prevention, which consists of acting on the socio-ecological environment or the living environment to neutralize the reservoirs of germs and vectors; and thus, avoid as much as possible the contact between the germs and the healthy subjects. Secondly, there is prophylactic prevention, which consists of taking preventive medication. The challenge here is to neutralize the invasion of pathogenic germs in the human body and avoid the conversion of the pathogen into pathology. The implementation of either or both paradigms depends on the type of infectious disease.

- The health promotion system

The health promotion system is an extension of prevention that should no longer be limited to acting on the pathogenic system only. It is also necessary to integrate mechanisms for improving the economic, social and cultural resilience of populations; because, poverty, and certain socio-cultural signatures, for example, limit the capacities of populations to fight against infectious diseases ^{38, 39, 40, 41, 42, 43}. Health promotion therefore refers, as [ ⁴⁴: p.1-2] specifies, to:

« un processus social et politique global, qui comprend non seulement des actions visant à renforcer les aptitudes et les capacités des individus mais également des mesures visant à changer la situation sociale, environnementale et économique, de façon à réduire ses effets négatifs sur la santé publique et sur la santé des personnes. La promotion de la santé est le processus qui consiste à permettre aux individus de mieux maîtriser les déterminants de la santé et d’améliorer ainsi leur santé. La participation de la population est essentielle dans toute action de promotion de la santé. ».

- The healing or curative system

The curative system refers to mechanisms for the clinical management of infected or sick people. Its purpose is to treat the sick as quickly and efficiently as possible; and thus, neutralize the source of dissemination of the germs that these constitute (in the case of contagious diseases for example). It integrates both infrastructure and technical platforms, inputs and drugs, as well as human resources and care protocols. The complexity of the curative system in the cities is linked to the insufficiency of the mechanisms and capacities of the urban systems for the health care supply in relation to the demand which is in perpetual growth ^{45, 46}. It is also dependent on the quality-cost-time mismatch of more and more expensive care services. The overloaded functioning of hospitals in the cities, the high cost of care, the time taken to seek care and the very duration of this care are all indicators of this inadequacy. One of the social responses is the multiplication of risky therapeutic itineraries and protocols, which constitutes a real gangrene. These include, for example, informal care, informal drug networks, traditional medicine, prophetic medicine, etc. which seriously jeopardize treatment ⁴⁷. These complexity factors favor the spread of infections by contamination and increase the epidemiological and socio-economic repercussions of infectious diseases in cities ^{48, 49, 50}. The geosystem of endemo-epidemiogenesis city incorporates these realities of the healthcare system that influence the dynamics of the emergence and spread of infectious diseases.

- The endemo-epidemiological surveillance system

Endemo-epidemiological surveillance is the set of systematic mechanisms and processes for the collection, analysis and interpretation of data on endemo-epidemies, as well as the local dissemination of inherent health information for the purposes of community awareness, planning strategy, decision support and public action ^{51, 52, 53}. It is not limited to the production of information on the epidemiological facies and the associated repercussions. For example, it integrates the monitoring of resistance to chemical vector control substances and to drugs. It is therefore a question of documenting and informing decision-makers and local populations on a daily basis about the situation of pathogenic, vulnerable and diffusing systems, as well as preventive, promotional and curative systems. Endemo-epidemiological monitoring, regarding the importance and challenges of the information provided, is positioned as the keystone of the effectiveness of public intervention or any response in an endemo-epidemiological situation ⁵⁴.

3. The Scientific Laws of the Urban Endemo-epidemiogenesis Geosystem

The geographic mobility of germs, or more generally, the socio-spatial dynamics of pathogens in the geosystem of endemo-epidemiogenesis is governed by the principle of causality. The standardization of cause-and-effect relationships materializing this principle has allowed the reconstitution of three scientific laws ^{17, 55, 56} which regulate the functioning of the geosystem.

The Law of Endemo-Epidemiogenic Contact systematizes the causal relationship between “germ-healthy subject contact” and “the emergence of the infectious disease associated with this germ”. It establishes and standardizes a causal link of the conversion of the pathogen into pathology. This Law states that: “Any physical contact between a pathogenic agent and a healthy subject is endemo-epidemiogenic»; because, this contact introduces in this healthy subject an infectious germ which generally knows an invasion in the organism of this one; this invasion is accompanied by the release of infected or toxins harmful to the human body ^{10, 22}. The body is attacked and the subject's immune system ends up coming into play. A set of interactions develops between this infection of pathogens and the resistivity of the natural immune system against a backdrop of a balance of power. At this stage, two scenarios arise; in the first, the immune system is stronger. The infection is immediately neutralized naturally and the subject does not know the disease. There was no conversion of the pathogen into pathology. The subject is however a healthy carrier. It is a reservoir of germs, and therefore, a detonating focus of the infectious disease and its spread. This physical contact at the base of this process turns out to be endemo-epidemiogenic. In the second case, the immune system is weaker. The infection is not naturally neutralized. It intensifies by causing the disease in the infected subject which is also a reservoir of germs. There has been a conversion of the pathogen into pathology. The initial physical contact is also endemo-epidemiogenic in this second scenario.

Ultimately, if there is an emergence of an infectious disease in a community, then, according to this scientific law, there has been contact between a healthy subject and a pathogen causing the infectious disease. The urban space, which is a place of agglomeration, mixing and promiscuity, proves to be very favorable to the multiplication of endemo-epidemiogenic contacts. This Scientific Law explains the high bacterial, parasitic, viral, mycotic or fungal prevalence in urban areas.

Endemo-epidemization refers to the geographic spread of infectious diseases. This mobility concerns, in principle, the pathogens that cause it. It is therefore the diffusion of the pathogenic system from one space to another. It is based on the Law of the invasion of healthy spaces according to which : «the pathogenic system moves geographically from infested spaces to healthy spaces; because, the latter always offer favorable living conditions and exert an attraction on the said system».

This attractiveness is observed at the individual level. In principle, the survival instinct leads individuals to search areas where infectious diseases are rife towards healthy areas. They at times move around with their soiled objects, equipment and materials, contaminating the reception areas. The infested space is said to be emitter or diffuser and the healthy space is said to be receiver.

In a nutshell, if there is geographical spread of an infectious disease, then, according to this scientific law, there has been a displacement of the pathogenic system from an infested area to a healthy area.

Cities are the sites of an intense phenomenon of landscape change following continual rearrangements of the living environment. This phenomenon is more generally associated with changes in the forms of occupation and enhancement of urban space. It is not only produced by human action, but it can also result from a natural hazard. It is at the origin of the socio-spatial instability of pathogens risk areas. The Law of the Mutability of Pathogenesis Spaces standardizes the cause-and-effect relationship between landscape dynamics and changes in the status, function and role of spaces at risk of pathogens in an urban environment. According to this law: « Under the effect of a natural or societal hazard of urban landscape dynamics, a space potentially unfavorable to the development of the pathogenic system can mutate and become a favorable space; similarly, a space potentially favorable to the development of the pathogenic system can mutate and become an unfavorable space ». The first type of mutation is in favor of the multiplication of detonating foci, and therefore, of endemo-epidemicization. The second type is rather in favor of the reduction of said outbreaks.

The functioning of the urban geosystem of endemo-epidemiogenesis is marked by permanent confrontations between the precursor and resilient systems that are the components. The detonation and geographical spread of an infectious disease results from the nature of these complex relationships of mistrust. The Law of geosystemic power relations standardizes the cause-and-effect relationships between this confrontation and the actual emergence of the infectious disease. According to this law, « Any situation of endemo-epidemiological risk in the city generates a set of power relations between the precursor and resilient systems of the urban geosystem of infectious diseases. If these ratios are in favor of precursor systems, endemo-epidemiogenesis and endemo-epidemization are recorded. If these reports are in favor of resilient systems, there is neutralization of the endemo-epidemiological chain and of the infectious disease».

The balance of power associated with any situation of endemo-epidemiological risk operates on two scales: spatial and temporal. According to the first scale, these relationships occur at different levels of spatial scale depending on the magnitude or geographic scope of the risk: the housing block, the neighborhood, the borough, the entire city. Whatever the case, there is always an epicenter, a focus serving as the starting point of the threat in the urban space. The context of failure of the public health system is favorable to the geographical spread of the health risk in all complexity linked to the urban fact. Three complex tandems of the spatial distribution of endemo-epidemies can be mentioned. The first tandem relates to the mono-pathological risk, the second to the poly-pathological risk and the third to temporality.

In a situation of mono-pathological risk the threat of the geographical spread of a single infectious disease, the spatial complexity of the health fact is dependent on the emergence of new foci of this same pathology following its distribution in the city. The urban sites of these different centers are places of confrontation between precursor and resilient systems. The intensity of the confrontation depends on the extent of the health risk as an articulation of the hazard and the vulnerability in the geographical site concerned ⁵⁷, then on the extent of the response of the resilient systems. The intersection of these two magnitudes makes it possible to define different levels of intensity of the balance of power. By way of illustration, low intensity reports are recorded in sites with low health risk. Medium intensity reports are observed in the medium health risk sites. High-intensity reports are recorded in high-risk sites... A more precise sanometric analysis can therefore be based on profiles of indicators previously defined to measure the level of endemo-epidemiological risk (N) at a given moment. in different urban sites, and measure the response levels of the resilient systems (N') in these sites at the same time. Each site will be characterized by a couple of magnitude level coordinates (N_risk; N'_response). These are also the coordinates of the intensity of the balance of power analyzed; values allowing, among other things, to determine and interpret the result or the nature of the balance of power. This result may be in favor of the precursor systems and augur the continuation of endemo-epidemicization. It can also be in favor of resilient systems and augur the regression, then the neutralization of the spread of the infectious disease. The intersection of these two measurements in these sites makes it possible to establish a curve of variation in the intensity of the power relations, to interpret the nature of the said relations (favorable or unfavorable), to rule on the effectiveness of the resilience and predict the phenomenon. A mapping of said intensities can also be established and serve as a decision-making aid.

In general, a phenomenon of quantitative, qualitative and geographical multipolarity of power relations is observed in the urban space. All the geographical poles of power relations form a spatial mesh of the endemo-epidemiogenesis of the infectious disease. This mesh is converted into a spatial framework of endemo-epidemiogenesis when there is an infinity of poles that merge. This fusion geographically homogenizes the risk in the city and transforms the entire urban space into a macro-pole of power relations around the infectious disease. Cities in sub-Saharan Africa, for example, are often subject to a spatial mesh of cholera in the event of an epidemiological outbreak; while they constitute spatial frameworks of urban malaria. Resilient systems are subject to the obligation to multiply their capacities relating to environmental and prophylactic prevention systems (if any) and health promotion in relation to the infectious disease concerned. This substantial increase in capacity also and above all concerns the curative system, which refers to the actual care of patients. It is therefore a question here of strengthening the technical platforms or increasing the capacities in human resources, infrastructure, equipment, materials, inputs, drugs... In practice, a contrast in favor of the hecatombs is rather observed ^{22, 58}. The rapid increase in care needs is contrasted by a weak dynamic in improving the capacities of an already failing urban public health system.

In a situation of poly-pathological risk, that is to say, the threat of the simultaneous geographical spread of several infectious diseases, the spatial complexity of the health fact is linked to the emergence of new outbreaks of each of these pathologies following their simultaneous spread in the city. Each infectious disease has a grid of urban sites hosting its foci. Some sites may harbor outbreaks of several diseases. This results in two profiles: mono-focal sprout sites and multifocal sprout sites. These different sites are places of confrontation between precursor and resilient systems. The mono-focal sites experience monoplex power relationships that can be structured according to the different levels of intensity mentioned above. The result is a quantitative, qualitative and geographical multipolarity of monoplex power relations. Multi-focal sites experience multiplex power relations. The sites hosting the pathogenic foci of two, three, four, five... different infectious diseases experience respectively duplex, triplex, quadruplex, quintuplex...; reports can also be structured according to different levels of intensity. A quantitative, qualitative and spatial multipolarity of multiplex power relations is also observed.

The city is the subject of two types of overlapping spatial grids. There is the monoplex spatial grid specific to each infectious disease and the multiplex spatial grid where the different infectious diseases listed are superimposed or articulated. Concretely, this last spatial mesh is duplex if it is two diseases, triplex if it is three diseases, quadruplex if it is four diseases, quintuplex if it is acts of five diseases… Moreover, the intensification of the process of epidemization produces an infinity of foci, and therefore, of geographical poles of power relations. The fusion of these poles generates a monoplex spatial frame for each pathology and a multiplex spatial frame for all pathologies. This last type of spatial frame is duplex, triplex, quadruplex, quintuplex…, if it is respectively two, three, four, five… diseases.

The complexity tandem relating to temporality concerns both mono-pathological and poly-pathological risk situations. In principle, the temporal scale is decisive in the emergence and spread of infectious diseases in the city ⁵⁴. These two phenomena have a start and an end; they are therefore part of precise temporalities. There is always an opportune time that influences all these processes. The conversion of the pathogen into pathology is triggered at the instant T of contact between the germs and the healthy subject. The geographical spread of this disease is also triggered at the moment T' when the balance of power is in favor of the precursor systems. Conversely, the break in the chain of propagation begins at time T'' when the balance of power is in favor of resilient systems.

Moreover, the action of each type of system is procedural and therefore takes place in different temporalities, each characterized by a set of specific conditions. These are the three main epidemiological phases namely: emergence/progression, stabilization and regression. Both precursor and resilient systems all experience these three phases marked by temporal variations in the balance of power. These variations induce frequent geographical reconfiguration of the endemo-epidemiological fact. A dynamic of appearance and disappearance, reappearance and cyclical re-disappearance of dissemination centers and clinical cases is observed according to the state of fluctuating power relations at each temporality, however small it may be. This internal dynamic at each epidemiological phase leads to the conclusion that the spatial meshes and frames of infectious diseases (monoplex or multiplex) are not frozen in time. All in all, temporality is the vector of a set of fluctuations in the balance of power contributing substantially to the complexification of the geo-system of endemo-epidemiogenesis, with perpetually renewed and recomposed impacts.

4. Formulation of the Theory of Urban Endemo-epidemiogenesis

The three scientific laws reconstituted in this study, namely, the law of endemo-epidemiogenic contact, the law of pathogenic invasion of healthy spaces and the law of the mutability of spaces of pathogenesis, make it possible to better understand the functioning of the geosystem of infectious diseases governs by the principle of causality in urban settings. They make certain effects deductible knowing the causes. They allow the abduction of certain causes from the observed effects. They make it possible to establish the links between the known causes and the recorded effects, thus making possible generalization by induction. In addition to a better understanding of the geosystem of infectious diseases, the capacities of deduction, abduction and induction of these three laws account for their ability to predict and forecast the functioning of said geosystem. All these characteristics make these three laws a scientific Theory. According to Parsons ⁶⁰, a Scientific Theory is a system of laws governing the working of a scientific fact or phenomenon based on the principle of causality. It is precisely the Theory of urban endemo-epidemiogenesis which is based on cause-and-effect relationships standardized in scientific laws to forge an explanatory corpus or a general explanatory hypothesis in the sense of Vorms ⁶¹ on the processes emergence and geographic spread of infectious diseases in urban areas.

Just like all theories, it is a tool that makes it possible to think about the scientific fact (urban endemo-epidemiogenesis), then to structure said thought. This structuring makes it possible to reconstruct and explain any similar scientific fact independently of the empirical context from which the tool was designed. It opens the way to prediction and forecasting thanks to a guiding principle and the orientations of the general statement of the theory.

The guiding principle of a theory is a logical meaning summarizing thought and governing the object of that general explanatory hypothesis; a logic of reasoning and action, a state of mind; a metadisciplinary logical construction according to Granger ⁶² which makes it possible to articulate and structure thought during the formulation and operationalization of a general explanatory hypothesis ⁶³. In the context of this study, the Urban Endemo-Epidemiogenesis Theory is governed by a guiding principle that:

« The genesis endemo-epidemic is a construct; the mathematical answer of the balance of power between the precursor and resilient systems of the urban geosystem of infectious diseases. ». This is the principle background that must guide any reasoning or any philosophy of action relating to this theory.

From the above guiding principle emerges the general statement of the theory of urban endemo-epidemiogenesis which states that:

«Urban endemo-epidemiogenesis is the process of emergence and spread of infectious diseases in the city. It is the product of a geosystem composed of two hemispheres, one “precursor” and the other “resilient”. The precursor hemisphere relates to all the devices, mechanisms and processes of emergence and spread of infectious diseases. It is composed of four precursor systems: pathogen, vulnerability, classic itineraries of dissemination and channels of dissemination. Its operation is retained by a structural apparatus. The structural apparatus is made up of the detonating socio-spatial framework (relevant to the pathogenic system), the socio-spatial framework for the convertibility of the pathogen into pathology (relevant to the vulnerability system), the 48 classic germ diffusion routes and the transmission channels. geographical spread of germs (related to the diffusion system). The functional apparatus is made up of a set of interactions between structural components. These interactions can be structured in 48 interactive diagrams, operating according to the 48 classic routes. They are based globally on the principle of causality, and are governed by the three scientific Laws: the Law of endemo-epidemiogenic contact, the Law of pathogenic invasion of healthy spaces, the Law of mutability of spaces of pathogenesis and the Law of geosystemic power relations. The resilient hemisphere relates to all the devices, mechanisms and processes for combating the emergence and spread of urban endemo-epidemies. It is composed of the four resilient-systems: preventive, promotional, curative and endemo-epidemiological surveillance.

The two hemispheres constantly confront each other. These geosystemic power relations generate two scenarios for each endemo-epidemiological risk situation. (i)- When the precursor hemisphere dominates because of the limitations of the urban public health system, there is endemo-epidemiogenesis and endemo-epidemization. This dual process is operationalized from the structural and functional apparatus defined above. (ii)- When the resilient hemisphere dominates thanks to the efficiency of the urban public health system, the threat is globally controlled from the neutralization of the cause-and-effect relationships between the four precursor systems or from the structural and functional above. The conversion of the pathogen into pathology can be recorded, but the few recorded cases are very quickly controlled and circumscribed, with a break in the chain of geographical distribution.

Geosystemic power relations are not fixed in space. The multiplication of sites-outbreaks with different magnitudes of detonation imposes a geographical variation of the response according to the situation of each urban site serving as a space of defiance or confrontation. The city is the subject of a spatial network of endemo-epidemiogenesis. The conversion of this mesh into a frame takes place when there is fusion of an infinity of poles of balance of power. The city becomes a spatial framework of endemo-epidemiogenesis. This reality in a situation of mono-pathology becomes more complex in a situation of poly-pathology marked by the simultaneous occurrence of several infectious diseases.

In this case, the city presents two profiles of sites at risk: the mono-focal sites of germs where a single type of power relationship develops and the multifocal sites of germs subject to several types of power relationships associated with the different rampant infectious diseases. In this situation of poly-pathology, the city is the subject of the superposition of two types of spatial meshes. There is the monoplex spatial mesh of each pathology and the multiplex spatial mesh that results from the intersection of all the infectious diseases that are rampant. This last spatial mesh is duplex, triplex, quadruplex, quintuplex, etc., when it comes to two, three, four, five, etc. pathologies respectively. In case of fusion of the infinity of detonator poles, and therefore, of inherent power relations, there is conversion of these meshes into duplex, triplex, quadruplex, quintuplex, etc. spatial frames, when it is a question of two, three, four, five, etc. diseases respectively.

Moreover, the geosystem of endemo-epidemiogenesis is not frozen in time. The different spatial grids and frameworks of infectious diseases (monoplex or multiplex) above correspond, in principle, to a precise instant of the endemo-epidemiological phenomenon. These spatial configurations evolve over time according to the changes experienced by each hemisphere and attributable to the confrontation. They are therefore a function of the fluctuations of the inter-hemispheric force ratios. Clearly, the functioning of the different hemispheres and the interactions between them are procedural. A chronological sequencing of this process leads to the definition of a series of temporalities of endemo-epidmiology. Each temporality corresponds to a specific geographical configuration of the geosystemic balance of power and of the endemo-epidemiological fact as a whole. A series of geographical configurations associated with the series of temporalities can therefore be established. There is therefore a correlation between “spatial configuration” and “temporality” which accounts for the predictability and predictability of endemo-epidemiogenesis.

Ultimately, three synthetic postulates can be formulated: (1)- Urban endemo-epidemiogenesis is a construct, a product of the articulation of power relations governed by cause-and-effect relationships between precursor and resilient systems in continued defiance in the urban infectious disease geosystem. (2)- Temporality constantly configures and reconfigures the precursor and resilient systems, and the balance of power between them, as well as the mutability of the spatial configuration of the endemo-epidemiological fact as a whole. (3)- Urban space, by its characteristics, is a socio-spatial order of heterogeneous, evolutionary and complex endemo-epidemiogenesis, unlike rural space which, also by its characteristics, is a socio-spatial order. Relatively homogeneous, fixed and simplex spatial endemo-epidemiogenesis. Figure 1 schematically reconstructs a logic or flowchart of theory.

5. Conclusion

The rapid urban development observed since the second half of the 20th century has imposed a reconfiguration of the geographical distribution of the world's population in favor of cities. These growing mutations probably lead to qualifying this period as the urbanocene, the era of urbanization and urbanity gradually making the earth an urban planet. This reality is accompanied by an acute complexity of the challenges underlying these socio-spatial technostructures (cities). Public health issues are, for example, a major problems in these socio-demographic frameworks that are difficult to control ^{64, 65}. The global city experiences substantially the same health precariousness linked to infectious patients who only change in type, form and extent from one geographical space to another, as well as within the same geographical space. ^{13, 66, 67, 68}.

The control of these pathologies as well as their foreseeability and their predictability remain however mortgaged by the complexity of the questions of public health in urban environment on the one hand, then by the insufficiency of the appropriate tools for this purpose on the other hand. This reality is the precursor of the present study which led to the development of a theory of urban endemo-epidemiogenesis, in addition to the theory of the in situ diffusion of germs in a natural environment of Ménard ¹² and the researches of Lindstrand, Bergström, Rosling, Rubenson, Stenson, Tylleskär ⁶⁹. In addition to being a general explanatory hypothesis, this theory is a tool for observation and deciphering, diagnosis and analysis of the endemo-epidemiological fact in urban areas. Due to its aptitude for forecasting and prediction, this tool is available as an instrument for planning and geostrategic decision-making in the fight against infectious diseases in the urban space that theory ultimately erects into a socio-spatial order of heterogeneous, evolutionary and complex endemo-epidemiogenesis, compared to the sensible homogeneity, stasis and simplexity of the rural space.

References