Differences in social activity increase efficiency of contact tracing

Digital contact tracing has been suggested as an effective strategy for controlling an epidemic without severely limiting personal mobility. Here, we use smartphone proximity data to explore how social structure affects contact tracing of COVID-19. We model the spread of COVID-19 and find that the effectiveness of contact tracing depends strongly on social network structure and heterogeneous social activity. Contact tracing is shown to be remarkably effective in a workplace environment and the effectiveness depends strongly on the minimum duration of contact required to initiate quarantine. In a realistic social network, we find that forward contact tracing with immediate isolation can reduce an epidemic by more than 70%. In perspective, our findings highlight the necessity of incorporating social heterogeneity into models of mitigation strategies. Graphic abstract

Lorenz von Stein und Hermann Heller als Ahnherren des deutschen Sozialstaats. Soziales Königtum und sozialer Rechtsstaat im Dienste der Freiheit

Lorenz von Stein und Hermann Heller können als Ahnherren des deutschen Sozialstaats verstanden werden. Ausgehend von einem hegelschen Staatsbegriff sind ihre Theorien vom Prinzip der Freiheit geleitet, das als Bedingung und als Ziel staatlicher Fürsorge dient. Im Kontext der Revolutionen von 1848 diagnostiziert Stein eine soziale Spaltung, welche für ihn die Gefahr eines immerwährenden Kriegs zwischen den Klassen birgt. In der Folge entwickelt er seine Theorie des sozialen Königtums, das die freie Selbstverwirklichung aller Bürger befördern soll. Heller führt die Instabilität der Weimarer Demokratie auf eine zu große soziale Heterogenität zurück, die er auf ökonomische Ungleichheit zurückführt. Durch die Weiterentwicklung des liberalen Staats zu einem sozialen Rechtsstaat soll die Integration aller Bürger in Staat, Nation und Kulturgemeinschaft ermöglicht werden. Lorenz von Stein and Hermann Heller can be understood as forefathers of the German welfare state. Based on a Hegelian concept of the state, their theories are guided by the principle of liberty that serves as condition and as goal of state welfare. In the context of the 1848 revolutions, Stein diagnoses a social division that could lead to perpetual war between the classes. Consequently, he develops his theory of social kingship, which serves to promote the free self-actualization of all citizens. Heller attributes the instability of Weimar democracy to excessive social heterogeneity caused by economic inequality. By developing the liberal state into a social constitutional state, he seeks to enable the integration of all citizens into state, nation and cultural community.

Kinetic models for epidemic dynamics with social heterogeneity

We introduce a mathematical description of the impact of the number of daily contacts in the spread of infectious diseases by integrating an epidemiological dynamics with a kinetic modeling of population-based contacts. The kinetic description leads to study the evolution over time of Boltzmann-type equations describing the number densities of social contacts of susceptible, infected and recovered individuals, whose proportions are driven by a classical SIR-type compartmental model in epidemiology. Explicit calculations show that the spread of the disease is closely related to moments of the contact distribution. Furthermore, the kinetic model allows to clarify how a selective control can be assumed to achieve a minimal lockdown strategy by only reducing individuals undergoing a very large number of daily contacts. We conduct numerical simulations which confirm the ability of the model to describe different phenomena characteristic of the rapid spread of an epidemic. Motivated by the COVID-19 pandemic, a last part is dedicated to fit numerical solutions of the proposed model with infection data coming from different European countries.

A Political and Ameliorative State of Nature

This chapter turns to Miranda Fricker’s genealogy of the virtue of testimonial justice and argues that her politicized state of nature illustrates how reverse-engineering can feed into conceptual engineering. The chapter first examines how she de-idealizes her state-of-nature model just enough to bring social heterogeneity and politics into it, thereby raising the question of how far genealogical models should be de-idealized. Second, it is shown how Fricker’s use of pragmatic genealogy differs from that of the other genealogists in being primarily ameliorative rather than explanatory. While earlier genealogists reverse-engineered the points of practices we already have, Fricker’s genealogy functions as a corrective, indicating respects in which our practices have in fact developed in ways that fall short of satisfying the needs highlighted by her model. It is then argued that making ameliorative use of the method requires pairing genealogy with a theory of error.

Social Heterogeneity Drives Complex Patterns of the COVID-19 Pandemic: Insights From a Novel Stochastic Heterogeneous Epidemic Model (SHEM)

In addition to vaccine and impactful treatments, mitigation strategies represent an effective way to combat the COVID-19 virus and an invaluable resource in this task is numerical modeling that can reveal key factors in COVID-19 pandemic development. On the other hand, it has become evident that regional infection curves of COVID-19 exhibit complex patterns which often differ from curves predicted by forecasting models. The wide variations in attack rate observed among different social strata suggest that this may be due to social heterogeneity not accounted for by regional models. We investigated this hypothesis by developing and using a new Stochastic Heterogeneous Epidemic Model that focuses on subpopulations that are vulnerable in the sense of having an increased likelihood of spreading infection among themselves. We found that the isolation or embedding of vulnerable sub-clusters in a major population hub generated complex stochastic infection patterns which included multiple peaks and growth periods, an extended plateau, a prolonged tail, or a delayed second wave of infection. Embedded vulnerable groups became hotspots that drove infection despite efforts of the main population to socially distance, while isolated groups suffered delayed but intense infection. Amplification of infection by these hotspots facilitated transmission from one urban area to another, causing the epidemic to hopscotch in a stochastic manner to places it would not otherwise reach; whereas vaccination only in hotspot populations stopped geographic spread of infection. Our results suggest that social heterogeneity is a key factor in the formation of complex infection propagation patterns. Thus, the mitigation and vaccination of vulnerable groups is essential to control the COVID-19 pandemic worldwide. The design of our new model allows it to be applied in future studies of real-world scenarios on any scale, limited only by computing memory and the ability to determine the underlying topology and parameters.

Chinese communities of Paris: Integration, preserving identity

The article examines specifics of integration of the Chinese diaspora into French society. The author identifies several Chinese communities, differing by the place of origin, such as «Indo-Chinese community» (from Southern Vietnam), «Wenzhou» (county in Zhejiang province), «Dongbei» (from the region of the same name of the PRC). The study reveals the influence of «push» («exodus» from Vietnam) and «pull» to the country of immigration («Wenzhou» and «Dongbei» communities) factors. The paper investigates social heterogeneity of the diaspora, from the «artisan proletariat» and small merchants to wholesalers and financiers. The author analyzes common features originating in cultural identity. The importance of ethno-cultural characteristics in the integration of the Chinese and their success (as a «model minority») is emphasized. The paper discusses the nature of anti-Chinese sentiments in French society (ressentiment). Using the case study of the Chinese diaspora, the author raises the question of the possibility of multicultural integration in contemporary France.

Cumani

This book is a synthesis of the great migrations of the 6th-13th centuries, focused on the median space between the two extremes of the Eurasian continent: Western Europe and Eastern Asia. In the light of the sources, it aims to reassess the complexity of the relationships between the nomads of the steppes and the sedentarized societies that came into contact with them. The choice to focus on the Qïpčaq-Cumans is due to their history, unique because they never constituted an organized and centralized center of collective power (stateless nomads); and paradigmatic, because it encompasses all the constitutive elements of steppe nomadism: social heterogeneity, mobility, military preparation, attraction for trade and willingness to negotiate. The migrations of the nomads of the steppes and their arrival close to the great organized communities of the Islamic and Christian world, from Asia to Europe, contributed to triggering a process of integration between Asia and the Mediterranean basin, a process that the Mongol invasion and conquest completed, giving birth to a new shared global space.

Social heterogeneity and the COVID-19 lockdown in a multi-group SEIR model

The goal of the lockdown is to mitigate and if possible prevent the spread of an epidemic. It consists in reducing social interactions. This is taken into account by the introduction of a factor of reduction of social interactions q, and by decreasing the transmission coefficient of the disease accordingly. Evaluating q is a difficult question and one can ask if it makes sense to compute an average coefficient q for a given population, in order to make predictions on the basic reproduction rate ℛ0, the dynamics of the epidemic or the fraction of the population that will have been infected by the end of the epidemic. On a very simple example, we show that the computation of ℛ0 in a heterogeneous population is not reduced to the computation of an average q but rather to the direct computation of an average coefficient ℛ0. Even more interesting is the fact that, in a range of data compatible with the Covid-19 outbreak, the size of the epidemic is deeply modified by social heterogeneity, as is the height of the epidemic peak, while the date at which it is reached mainly depends on the average ℛ0 coefficient. This paper illustrates more technical results that can be found in [4], with new numerical computations. It is intended to draw the attention on the role of heterogeneities in a population in a very simple case, which might be difficult to apprehend in more realistic but also more complex models.