Stability of Piecewise Deterministic Markovian Metapopulation Processes on Networks

The purpose of this paper is to study a Markovian metapopulation model on a directed graph with edge-supported transfers and deterministic intra-nodal population dynamics. We first state tractable stability conditions for two typical frameworks motivated by applications: constant jump rates with multiplicative transfer amplitudes, and coercive jump rates with unitary transfers. More general criteria for boundedness, petiteness and ergodicity are then given

Estimating Chikungunya prevalence in La Réunion Island outbreak by serosurveys: Two methods for two critical times of the epidemic

<p>Abstract</p> <p>Background</p> <p>Chikungunya virus (CHIKV) caused a major two-wave seventeen-month-long outbreak in La Réunion Island in 2005–2006. The aim of this study was to refine clinical estimates provided by a regional surveillance-system using a two-stage serological assessment as gold standard.</p> <p>Methods</p> <p>Two serosurveys were implemented: first, a rapid survey using stored sera of pregnant women, in order to assess the attack rate at the epidemic upsurge (s1, February 2006; n = 888); second, a population-based survey among a random sample of the community, to assess the herd immunity in the post-epidemic era (s2, October 2006; n = 2442). Sera were screened for anti-CHIKV specific antibodies (IgM and IgG in s1, IgG only in s2) using enzyme-linked immunosorbent assays. Seroprevalence rates were compared to clinical estimates of attack rates.</p> <p>Results</p> <p>In s1, 18.2% of the pregnant women were tested positive for CHIKV specific antibodies (13.8% for both IgM and IgG, 4.3% for IgM, 0.1% for IgG only) which provided a congruent estimate with the 16.5% attack rate calculated from the surveillance-system. In s2, the seroprevalence in community was estimated to 38.2% (95% CI, 35.9 to 40.6%). Extrapolations of seroprevalence rates led to estimate, at 143,000 and at 300,000 (95% CI, 283,000 to 320,000), the number of people infected in s1 and in s2, respectively. In comparison, the surveillance-system estimated at 130,000 and 266,000 the number of people infected for the same periods.</p> <p>Conclusion</p> <p>A rapid serosurvey in pregnant women can be helpful to assess the attack rate when large seroprevalence studies cannot be done. On the other hand, a population-based serosurvey is useful to refine the estimate when clinical diagnosis underestimates it. Our findings give valuable insights to assess the herd immunity along the course of epidemics.</p

À l’école de la ville : contre-cultures expérimentales dans les années 1970

Cet article propose le récit de trois expérimentations pédagogiques et artistiques des années 1970, défricheuses pour bâtir un contre-modèle face aux écoles, lieux d’enfermement des enfants et de leurs apprentissages. À partir des ateliers de rue de Riccardo Dalisi de 1971 à 1974 à Naples avec des enfants déscolarisés, nous verrons comment des architectes, artistes, designers, proposent la réintroduction des enfants dans la rue et les espaces publics de quartiers populaires.This article proposes the account of three pedagogical and artistic experimentation of the 1970s, pioneers in building a counter-model to schools, places of confinement for children and their learning. Starting from Riccardo Dalisi’s street workshops from 1971 to 1974 in Naples with children who had dropped out of school, we will see how architects, artists and designers propose the reintroduction of children into the street and public spaces of working-class neighborhoods

Real-Time Assessment of Health-Care Requirements During the Zika Virus Epidemic in Martinique.

The spread of Zika virus in the Americas has been associated with a surge in Guillain-Barré syndrome (GBS) cases. Given the severity of GBS, territories affected by Zika virus need to plan health-care resources to manage GBS patients. To inform such planning in Martinique, we analyzed Zika virus surveillance and GBS data from Martinique in real time with a modeling framework that captured dynamics of the Zika virus epidemic, the risk of GBS in Zika virus-infected persons, and the clinical management of GBS cases. We compared our estimates with those from the 2013-2014 Zika virus epidemic in French Polynesia. We were able to predict just a few weeks into the epidemic that, due to lower transmission potential and lower probability of developing GBS following infection in Martinique, the total number of GBS cases in Martinique would be substantially lower than suggested by simple extrapolations from French Polynesia. We correctly predicted that 8 intensive-care beds and 7 ventilators would be sufficient to treat GBS cases. This study showcased the contribution of modeling to inform local health-care planning during an outbreak. Timely studies that estimate the proportion of infected persons that seek care are needed to improve the predictive power of such approaches

Minimising school disruption under high incidence conditions due to the Omicron variant in France, Switzerland, Italy, in January 2022.

BackgroundAs record cases of Omicron variant were registered in Europe in early 2022, schools remained a vulnerable setting undergoing large disruption.AimThrough mathematical modelling, we compared school protocols of reactive screening, regular screening, and reactive class closure implemented in France, in Baselland (Switzerland), and in Italy, respectively, and assessed them in terms of case prevention, testing resource demand, and schooldays lost.MethodsWe used a stochastic agent-based model of SARS-CoV-2 transmission in schools accounting for within- and across-class contacts from empirical contact data. We parameterised it to the Omicron BA.1 variant to reproduce the French Omicron wave in January 2022. We simulated the three protocols to assess their costs and effectiveness for varying peak incidence rates in the range experienced by European countries.ResultsWe estimated that at the high incidence rates registered in France during the Omicron BA.1 wave in January 2022, the reactive screening protocol applied in France required higher test resources compared with the weekly screening applied in Baselland (0.50 vs 0.45 tests per student-week), but achieved considerably lower control (8% vs 21% reduction of peak incidence). The reactive class closure implemented in Italy was predicted to be very costly, leading to > 20% student-days lost.ConclusionsAt high incidence conditions, reactive screening protocols generate a large and unplanned demand in testing resources, for marginal control of school transmissions. Comparable or lower resources could be more efficiently used through weekly screening. Our findings can help define incidence levels triggering school protocols and optimise their cost-effectiveness

Interplay between competitive and cooperative interactions in a three-player pathogen system

In ecological systems, heterogeneous interactions between pathogens take place simultaneously. This occurs, for instance, when two pathogens cooperate, while at the same time, multiple strains of these pathogens co-circulate and compete. Notable examples include the cooperation of human immunodeficiency virus with antibiotic-resistant and susceptible strains of tuberculosis or some respiratory infections with Streptococcus pneumoniae strains. Models focusing on competition or cooperation separately fail to describe how these concurrent interactions shape the epidemiology of such diseases. We studied this problem considering two cooperating pathogens, where one pathogen is further structured in two strains. The spreading follows a susceptible-infected-susceptible process and the strains differ in transmissibility and extent of cooperation with the other pathogen. We combined a mean-field stability analysis with stochastic simulations on networks considering both well-mixed and structured populations. We observed the emergence of a complex phase diagram, where the conditions for the less transmissible, but more cooperative strain to dominate are non-trivial, e.g. non-monotonic boundaries and bistability. Coupled with community structure, the presence of the cooperative pathogen enables the coexistence between strains by breaking the spatial symmetry and dynamically creating different ecological niches. These results shed light on ecological mechanisms that may impact the epidemiology of diseases of public health concern

La Пότνια θηρῶν ou les frontières de l’Autre. Réflexion archéologique sur la signification d’une image homérique en Grèce orientalisante

Les historiens de la religion grecque ont depuis longtemps perçu l’existence d’une divinité des temps préhelléniques d’origine égéo-anatolienne, la maîtresse des animaux, dont le thème iconographique connaît un regain d’intérêt dans différentes productions artistiques du monde grec à la période dite orientalisante (fin VIIIe-milieu VIe siècle av. J.-C.). Dès la fin du XIXe siècle, cette image singulière fut mise en relation directe avec la protectrice du monde sauvage, Artémis, d’après l’expression πότνια θηρῶν, employée par Homère pour qualifier la déesse au chant XXI de l’Iliade. Dès lors, la maîtresse des animaux fut interprétée comme une préfiguration de la déesse Artémis, progressivement assimilée au cours du VIe siècle av. J.-C. à la jumelle olympienne. Ce rapprochement univoque avec la personnalité complexe et ambiguë d’Artémis requiert d’être reconsidéré à la lumière d’un travail contextuel conciliant l’approche iconographique et l’approche archéologique, en s’appuyant en particulier sur une redéfinition du répertoire des images étudiées et une révision de leurs associations cultuelles.Historians of Greek religion have for a long time been aware of the existence of a deity of pre-Hellenic times of Aegean-Anatolian origins, the mistress of animals and in whose iconographic theme there was a resurgence of interest in various artistic productions in the Greek world during the so-called orientalizing period (end 8th – mid 6th century B.C.). In the late 19th century, this particular image was linked to the protector of the wild world, Artemis, following the expression, πότνια θηρῶν, used by Homer in book XXI of the Iliad to describe the goddess. Since then, the mistress of animals has been interpreted as a forerunner of the goddess Artemis, gradually assimilated with the Olympian twin in the 6th century BC. This unequivocal connection with the complex and ambiguous personality of Artemis needs to be reconsidered in the light of a contextual study using both an iconographic and an archaeological approach, relying especially on a redefining of the inventory of the images studied and a review of their cultic associations