Optimizing topological cascade resilience based on the structure of terrorist networks

Complex socioeconomic networks such as information, finance and even terrorist networks need resilience to cascades - to prevent the failure of a single node from causing a far-reaching domino effect. We show that terrorist and guerrilla networks are uniquely cascade-resilient while maintaining high efficiency, but they become more vulnerable beyond a certain threshold. We also introduce an optimization method for constructing networks with high passive cascade resilience. The optimal networks are found to be based on cells, where each cell has a star topology. Counterintuitively, we find that there are conditions where networks should not be modified to stop cascades because doing so would come at a disproportionate loss of efficiency. Implementation of these findings can lead to more cascade-resilient networks in many diverse areas.Comment: 26 pages. v2: In review at Public Library of Science ON

Arbitrage opportunities in CDS term structure: theory and implications for OTC derivatives

Absence-of-Arbitrage (AoA) is the basic assumption underpinning derivatives pricing theory. As part of the OTC derivatives market, the CDS market not only provides a vehicle for participants to hedge and speculate on the default risks of corporate and sovereign entities, it also reveals important market-implied default-risk information concerning the counterparties with which financial institutions trade, and for which these financial institutions have to calculate various valuation adjustments (collectively referred to as XVA) as part of their pricing and risk management of OTC derivatives, to account for counterparty default risks. In this study, we derive No-arbitrage conditions for CDS term structures, first in a positive interest rate environment and then in an arbitrary one. Using an extensive CDS dataset which covers the 2007-09 financial crisis, we present a catalogue of 2,416 pairs of anomalous CDS contracts which violate the above conditions. Finally, we show in an example that such anomalies in the CDS term structure can lead to persistent arbitrage profits and to nonsensical default probabilities. The paper is a first systematic study on CDS-term-structure arbitrage providing model-free AoA conditions supported by ample empirical evidence

Compartmental models for seasonal hyperendemic bacterial meningitis in the African meningitis belt

International audienceThe pathophysiological mechanisms underlying the seasonal dynamic and epidemic occurrence of bacterial meningitis in the African meningitis belt remain unknown. Regular seasonality (seasonal hyperendemicity) is observed for both meningococcal and pneumococcal meningitis and understanding this is critical for better prevention and modelling. The two principal hypotheses for hyperendemicity during the dry season imply (1) an increased risk of invasive disease given asymptomatic carriage of meningococci and pneumococci; or (2) an increased transmission of these bacteria from carriers and ill individuals. In this study, we formulated three compartmental deterministic models of seasonal hyperendemicity, featuring one (model1-‘inv’ or model2-‘transm’), or a combination (model3-‘inv-transm’) of the two hypotheses. We parameterised the models based on current knowledge on meningococcal and pneumococcal biology and pathophysiology. We compared the three models' performance in reproducing weekly incidences of suspected cases of acute bacterial meningitis reported by health centres in Burkina Faso during 2004–2010, through the meningitis surveillance system. The three models performed well (coefficient of determination R2, 0.72, 0.86 and 0.87, respectively). Model2-‘transm’ and model3-‘inv-transm’ better captured the amplitude of the seasonal incidence. However, model2-‘transm’ required a higher constant invasion rate for a similar average baseline transmission rate. The results suggest that a combination of seasonal changes of the risk of invasive disease and carriage transmission is involved in the hyperendemic seasonality of bacterial meningitis in the African meningitis belt. Consequently, both interventions reducing the risk of nasopharyngeal invasion and the bacteria transmission, especially during the dry season are believed to be needed to limit the recurrent seasonality of bacterial meningitis in the meningitis belt

Burden of the Disease and Management in COVID-19 Hospitalized Patients in MSO and Home Care in France: COVID-Hosp Study (2020-2022) - EPH178

International audienceObjectivesThis study aims to assess the burden of the disease and management in medical, surgical and obstetrics (MSO) and home care (HC) hospitalizations for COVID-19 in France (2020-2022) by patients’ risk status and epidemic waves.MethodsThis is a retrospective study based on French national hospital database (PMSI). All patients hospitalized for COVID-19 (MSO or HC) were identified between 2020 and 2022. The disease management includes the admissions in intensive care unit (ICU) and the use of mechanical ventilation (MV) during the hospitalization. High-risk patients (HRP) were defined according to the French HTA methodology. Epidemic waves were defined according to the incidence peak observed. Mortality is based on deaths during hospital stays.ResultsOverall, 800,093 admissions for COVID-19 (97% MSO) and 687,027 patients were recorded. A peak in HC hospitalizations was observed in 2020 (14,117), followed by a decrease of 40% per year. In MSO, the peak occurs in 2021 (300,813), followed by a decrease of 27% in 2022. The average age was 65 (±22) years in MSO and 85 (±13) years in HC. The proportion of hospitalizations of HRP in MSO was between 62% and 78% depending on the year. Conversely, the proportion of HRP remains constant over time in HC, around 95%. The most observed HRP sub-group was the elderly patients (65+). The most important epidemic wave (alpha variant) was observed between March-April 2021 (132,104 hospitalizations). Among MSO hospitalizations 17% were managed in ICU, including 40.3% with MV. The proportions were similar between HRP sub-groups. Death proportion was between 9.7% and 33.1% depending on the disease management and was systematically higher in HRP.ConclusionsThis study provided a national understanding of the clinical burden of COVID-19 in the French hospital system, which were congested during the crisis. Economic burden and the role of the vaccination remains to be assessed

Increased incidence of acute parvovirus B19 infections in Marseille, France, in 2012 compared with the 2002–2011 period

AbstractHuman parvovirus B19 occurs worldwide and causes mild or asymptomatic disease in the form of cyclic local epidemics usually occurring in late winter and early summer. In 2012, a dramatic increase in cases was observed in the Public hospitals system of Marseille, with a total of 53 cases reported. Here, we describe the characteristics of this outbreak and compare it with the local epidemiology of B19V infections observed during the 2002–2011 period