A Bag of Expression framework for improved human action recognition

The Bag of Words (BoW) approach has been widely used for human action recognition in recent state-of-the-art methods. In this paper, we introduce what we call a Bag of Expression (BoE) framework, based on the bag of words method, for recognizing human action in simple and realistic scenarios. The proposed approach includes space time neighborhood information in addition to visual words. The main focus is to enhance the existing strengths of the BoW approach like view independence, scale invariance and occlusion handling. BOE includes independent pairs of neighbors for building expressions, therefore it is tolerant to occlusion and capable of handling view independence up to some extent in realistic scenarios. Our main contribution includes learning a class specific visual words extraction approach for establishing a relationship between these extracted visual words in both space and time dimension. Finally, we have carried out a set of experiments to optimize different parameters and compare its performance with recent state-of-the-art-methods. Our approach outperforms existing Bag of Words based approaches, when evaluated using the same performance evaluation methods. We tested our approach on four publicly available datasets for human action recognition i.e. UCF-Sports, KTH, UCF11 and UCF50 and achieve significant results i.e. 97.3%, 99.5%, 96.7% and 93.42% respectively in terms of average accuracy.Sergio A Velastin has received funding from the Universidad Carlos III de Madrid, the European Unions Seventh Framework Programme for research, technological development and demonstration under grant agreement nº 600371, el Ministerio de Economía, Industria y Competitividad (COFUND2013-51509) el Ministerio de Educación, Cultura y Deporte (CEI-15-17) and Banco Santander

Impact of Zika Virus Emergence in French Guiana: A Large General Population Seroprevalence Survey.

BACKGROUND: Since the identification of Zika virus (ZIKV) in Brazil in May 2015, the virus has spread throughout the Americas. However, ZIKV burden in the general population in affected countries remains unknown. METHODS: We conducted a general population survey in the different communities of French Guiana through individual interviews and serologic survey during June-October 2017. All serum samples were tested for anti-ZIKV immunoglobulin G antibodies using a recombinant antigen-based SGERPAxMap microsphere immunoassay, and some of them were further evaluated through anti-ZIKV microneutralization tests. RESULTS: The overall seroprevalence was estimated at 23.3% (95% confidence interval [CI], 20.9%-25.9%) among 2697 participants, varying from 0% to 45.6% according to municipalities. ZIKV circulated in a large majority of French Guiana but not in the most isolated forest areas. The proportion of reported symptomatic Zika infection was estimated at 25.5% (95% CI, 20.3%-31.4%) in individuals who tested positive for ZIKV. CONCLUSIONS: This study described a large-scale representative ZIKV seroprevalence study in South America from the recent 2015-2016 Zika epidemic. Our findings reveal that the majority of the population remains susceptible to ZIKV, which could potentially allow future reintroductions of the virus

Spatial Distribution and Burden of Emerging Arboviruses in French Guiana.

Despite the health, social and economic impact of arboviruses in French Guiana, very little is known about the extent to which infection burden is shared between individuals. We conducted a large multiplexed serological survey among 2697 individuals from June to October 2017. All serum samples were tested for IgG antibodies against DENV, CHIKV, ZIKV and MAYV using a recombinant antigen-based microsphere immunoassay with a subset further evaluated through anti-ZIKV microneutralization tests. The overall DENV seroprevalence was estimated at 73.1% (70.6-75.4) in the whole territory with estimations by serotype at 68.9% for DENV-1, 38.8% for DENV-2, 42.3% for DENV-3, and 56.1% for DENV-4. The overall seroprevalence of CHIKV, ZIKV and MAYV antibodies was 20.3% (17.7-23.1), 23.3% (20.9-25.9) and 3.3% (2.7-4.1), respectively. We provide a consistent overview of the burden of emerging arboviruses in French Guiana, with useful findings for risk mapping, future prevention and control programs. The majority of the population remains susceptible to CHIKV and ZIKV, which could potentially facilitate the risk of further re-emergences. Our results underscore the need to strengthen MAYV surveillance in order to rapidly detect any substantial changes in MAYV circulation patterns

Reconstructing Mayaro virus circulation in French Guiana shows frequent spillovers

Funder: This study was supported by the “European Regional Development Fund” under EPI-ARBO grant agreement (GY0008695), the “Regional Health Agency of French Guiana”, the “National Center of Spatial Studies”. CF acknowledges funding from Calmette and Yersin allocated by the “Pasteur Institut Department of International Affairs”. N.H. and S.C. acknowledge financial support from the AXA Research Fund, the Investissement d’Avenir program, the Laboratoire d’Excellence Integrative Biology of Emerging Infectious Diseases program (Grant ANR-10-LABX-62-IBEID), the Models of Infectious Disease Agent Study of the National Institute of General Medical Sciences, the INCEPTION project (PIA/ANR-16-CONV-0005), the European Union’s Horizon 2020 research and innovation programme under ZIKAlliance grant agreement No 734548.Abstract: Characterizing the circulation of Mayaro virus (MAYV), an emerging arbovirus threat, is essential for risk assessment but challenging due to cross-reactivity with other alphaviruses such as chikungunya virus (CHIKV). Here, we develop an analytical framework to jointly assess MAYV epidemiology and the extent of cross-reactivity with CHIKV from serological data collected throughout French Guiana (N = 2697). We find strong evidence of an important sylvatic cycle for MAYV with most infections occurring near the natural reservoir in rural areas and in individuals more likely to go to the forest (i.e., adult males) and with seroprevalences of up to 18% in some areas. These findings highlight the need to strengthen MAYV surveillance in the region and showcase how modeling can improve interpretation of cross-reacting assays

Perceptions and behaviours associated with emerging arboviruses in French Guiana

Les arboviroses représentent un problème majeur de santé publique qui n’a cessé de prendre de l’ampleur au cours des dernières décennies. Récemment, les virus du chikungunya et du zika ont fait l’objet d’une attention particulière compte tenu de leur rapide expansion géographique et de leur haut potentiel épidémique. La compréhension des facteurs socio-comportementaux des populations face à ces maladies représente un intérêt majeur pour l’amélioration des campagnes de prévention de lutte anti-vectorielle. Nous avons abordé dans le cadre de cette thèse les perceptions et les comportements de la population guyanaise face à l’émergence du chikungunya et du zika et les avons mis en relation avec l’infection réelle des individus par un de ces arbovirus. Nous avons pour cela réalisé trois enquêtes, une en milieu scolaire lors de l’émergence du chikungunya, une chez les adultes lors de l’émergence du zika, et une enquête de séroprévalence en population générale à distance des épidémies. Nos résultats suggèrent l’existence d’une distribution sociodémographique et socio-économique dans les perceptions des risques associés au zika et au chikungunya. Nous avons montré que l’adoption de comportements de protection et la probabilité d’infection par un arbovirus apparaissent comme des processus multifactoriels qui dépendent aussi bien de variables socio-économiques, qu’environnementales et cognitives. D’une manière générale, la situation épidémiologique est susceptible de moduler les perceptions et les comportements de protection. Ces résultats ont permis d’identifier des groupes d’individus prioritaires pour les futurs programmes de prévention incluant préférentiellement les individus de plus de 60 ans, issus de populations défavorisées ou vivant dans certaines communes du Maroni ou de l’Oyapock pouvant être particulièrement impactées par les épidémies. Par ailleurs, ils ont mis en évidence l’impact collectif des comportements sur le risque d’infection individuel. Ces travaux soulignent enfin la nécessité de continuer les actions de santé publique, bien après les périodes de début d’épidémie fréquemment associées à une forte couverture médiatique, afin de maintenir un niveau de protection constant durant la période de forte transmission. La mise en place d’études longitudinales devrait permettre dans le futur, de mieux investiguer la dynamique spatio-temporelle des perceptions du risque associé aux arboviroses mais également des comportements de protection. spatio-temporelle des perceptions du risque associé aux arboviroses mais également des comportements de protection.For decades, arbovirus infection remained an important public health concern. Recently, considering their rapid geographic spread and high epidemic potential, chikungunya and zika viruses raised attention. Understanding socio-behavioural factors associated with these diseases among affected populations is crucial to improve vector control campaigns. This thesis studied risk perceptions associated with arboviruses and behaviour among population from French Guiana during the emergence of chikungunya and zika. Our analysis focused simultaneously on these factors and the real infection of dengue, chikungunya or zika viruses from seroprevalence data. We conducted three surveys, one among high school students during the emergence of chikungunya virus, the second among adult while zika virus emerged, and the third was a seroprevalence survey conducted among the general population, far from last epidemics. Our results suggest a socio demographic and a socio-economic distribution within risk perceptions associated with chikungunya and zika infections. Furthermore, these results revealed that the adoption of protective behaviours and the probability of contamination by an arbovirus is a multi-factorial process that depends on socio-cultural, environmental and cognitive factors. We also showed that epidemiologic context could impact perceptions and behaviours. Moreover, this thesis identify main groups for future prevention campaign targeting person aged 60 years old and more, from disadvantaged background, or living in affected villages across the Maroni or the Oyapock river. Findings also revealed the behavioural collective impact on the individual risk of infection we highlighted the need to extend public health actions after the beginning of the outbreak, period that is often exposed to important media coverage, to sustain protection during the period of high transmission. Longitudinal studies are therefore needed, to better investigate spatio-temporal dynamic of risk perceptions associated with arboviral infection and also protective behaviour

Connaissances, attitudes et pratiques des lycéens face à l’émergence du Chikungunya en Guyane

National audienc

Knowledge, Attitude and Practices of Vector-Borne Disease Prevention during the Emergence of a New Arbovirus: Implications for the Control of Chikungunya Virus in French Guiana

International audienceBackgroundDuring the last decade, French Guiana has been affected by major dengue fever outbreaks. Although this arbovirus has been a focus of many awareness campaigns, very little information is available about beliefs, attitudes and behaviors regarding vector-borne diseases among the population of French Guiana. During the first outbreak of the chikungunya virus, a quantitative survey was conducted among high school students to study experiences, practices and perceptions related to mosquito-borne diseases and to identify socio-demographic, cognitive and environmental factors that could be associated with the engagement in protective behaviors.Methodology/Principal FindingsA cross-sectional survey was administered in May 2014, with a total of 1462 students interviewed. Classrooms were randomly selected using a two-stage selection procedure with cluster samples. A multiple correspondence analysis (MCA) associated with a hierarchical cluster analysis and with an ordinal logistic regression was performed. Chikungunya was less understood and perceived as a more dreadful disease than dengue fever. The analysis identified three groups of individual protection levels against mosquito-borne diseases: “low” (30%), “moderate” (42%) and “high” (28%)”. Protective health behaviors were found to be performed more frequently among students who were female, had a parent with a higher educational status, lived in an individual house, and had a better understanding of the disease.Conclusions/SignificanceThis study allowed us to estimate the level of protective practices against vector-borne diseases among students after the emergence of a new arbovirus. These results revealed that the adoption of protective behaviors is a multi-factorial process that depends on both sociocultural and cognitive factors. These findings may help public health authorities to strengthen communication and outreach strategies, thereby increasing the adoption of protective health behaviors, particularly in high-risk populations.Author SummaryAlthough dengue fever has been a focus of many awareness campaigns in Latin America, very little information is available about beliefs, attitudes and behaviors regarding vector-borne diseases among the population of French Guiana. At the initial onset of the first chikungunya outbreak, a quantitative survey was conducted among 1462 high school students aiming to study experiences, practices and perceptions related to mosquito-borne diseases and to identify factors that could be associated with protective behaviors. Chikungunya was less understood and perceived as a more dreadful disease than dengue fever. Students were clustered in three different groups according to their level of protection: “low” (30%), “moderate” (42%) and “high” (28%). Protective health behaviors were found to be performed more frequently among students who were female, lived with a parent who had a higher educational status, lived in an individual house, and had a better understanding of the disease. The results revealed that the adoption of protective behaviors is a multi-factorial process that depends on both socio-economic and cognitive factors. These findings may help the public health authorities to strengthen their communication and outreach strategy, thereby increasing the adoption of protective health behaviors, particularly in endemic countries and high-risk populations

Map of French Guiana, South America, datasource: OpenStreetMap; QGIS 2.18 software.

<p>Map of French Guiana, South America, datasource: OpenStreetMap; QGIS 2.18 software.</p

Mean threat perception scores regarding dengue, chikungunya andz ika infections in French Guiana, 2016.

<p>Mean threat perception scores regarding dengue, chikungunya andz ika infections in French Guiana, 2016.</p

Risk perceptions and behaviors associated with zika disease among women and men according to different subgroups, French Guiana, 2016.

<p>Risk perceptions and behaviors associated with zika disease among women and men according to different subgroups, French Guiana, 2016.</p