title: Evaluation of a Multivariate Syndromic Surveillance System for West Nile Virus.
abstract: Various methods are currently used for the early detection of West Nile virus (WNV) but their outputs are not quantitative and/or do not take into account all available information. Our study aimed to test a multivariate syndromic surveillance system to evaluate if the sensitivity and the specificity of detection of WNV could be improved.
  
  
  
  Weekly time series data on nervous syndromes in horses and mortality in both horses and wild birds were used. Baselines were fitted to the three time series and used to simulate 100 years of surveillance data. WNV outbreaks were simulated and inserted into the baselines based on historical data and expert opinion. Univariate and multivariate syndromic surveillance systems were tested to gauge how well they detected the outbreaks; detection was based on an empirical Bayesian approach. The systems' performances were compared using measures of sensitivity, specificity, and area under receiver operating characteristic curve (AUC).
  
  
  
  When data sources were considered separately (i.e., univariate systems), the best detection performance was obtained using the data set of nervous symptoms in horses compared to those of bird and horse mortality (AUCs equal to 0.80, 0.75, and 0.50, respectively). A multivariate outbreak detection system that used nervous symptoms in horses and bird mortality generated the best performance (AUC = 0.87).
  
  
  
  The proposed approach is suitable for performing multivariate syndromic surveillance of WNV outbreaks. This is particularly relevant, given that a multivariate surveillance system performed better than a univariate approach. Such a surveillance system could be especially useful in serving as an alert for the possibility of human viral infections. This approach can be also used for other diseases for which multiple sources of evidence are available.
authors.affiliation: 1 INRA UR0346 Animal Epidemiology , VetagroSup, Marcy l'Etoile, France .
authors.forename: Céline
authors.initials: C
authors.lastname: Faverjon
authors.affiliation: 2 Department of Chemistry, Environment and Feed Hygiene, The National Veterinary Institute , Uppsala, Sweden .
authors.forename: M Gunnar
authors.initials: MG
authors.lastname: Andersson
authors.affiliation: 3 Office National de la Chasse et de la Faune Sauvage, Direction des Études et de la Recherche , Auffargis, France .
authors.forename: Anouk
authors.initials: A
authors.lastname: Decors
authors.affiliation: 4 ANSES Dozulé Laboratory for Equine Diseases , Dozulé, France .
authors.forename: Jackie
authors.initials: J
authors.lastname: Tapprest
authors.affiliation: 5 Clinique Vétérinaire, Collège Syndrome Nerveux du RESPE et Commission Maladies Infectieuses de l'AVEF , Faulquemont, Caen, France .
authors.forename: Pierre
authors.initials: P
authors.lastname: Tritz
authors.affiliation: 6 Centre de Recherche Pour la Conservation des Zones Humides Méditerranéennes , Fondation Tour du Valat, Arles, France .|7 UFR Sciences, Aix-Marseille University , Marseille, France .
authors.forename: Alain
authors.initials: A
authors.lastname: Sandoz
authors.affiliation: 8 Hungarian Academy of Sciences-Szent Istvan University (MTA-SZIE) Large Animal Clinical Research Group , Ullo, Dóra major, Hungary .
authors.forename: Orsolya
authors.initials: O
authors.lastname: Kutasi
authors.affiliation: 9 ANSES-Lyon , Epidemiology Unit, Lyon, France .
authors.forename: Carole
authors.initials: C
authors.lastname: Sala
authors.affiliation: 10 INRA UR0346 Animal Epidemiology et Département Hippique , VetAgroSup, Marcy L'Etoile, France .|11 Réseau d'Epidémio-Surveillance en Pathologie Equine (RESPE) , Caen, France .
authors.forename: Agnès
authors.initials: A
authors.lastname: Leblond
mesh_terms: D000818:Animals; D000835:Animals, Wild; D001715:Bird Diseases / Q000401:mortality*; D001717:Birds; D002493:Central Nervous System Diseases / Q000453:epidemiology / Q000662:veterinary*; D005602:France / Q000453:epidemiology; D006734:Horse Diseases / Q000401:mortality*; D006736:Horses; D006801:Humans; D011159:Population Surveillance / Q000379:methods; D014901:West Nile Fever / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology
keywords: Bayes; Horses; Multivariate detection; Syndromic surveillance; West Nile