title: A cluster study of predictors of severe West Nile virus infection.
abstract: OBJECTIVE
  To assess the value of multifocal chorioretinitis and of clinical manifestations and biologic parameters in the diagnosis of West Nile virus (WNV) infection.
  
  
  METHODS
  We conducted a prospective, controlled case series study during an outbreak of WNV infection between August 15 and October 24, 2003, of 64 consecutive patients who presented with clinical manifestations consistent with WNV disease. In each patient, standardized clinical and biologic data were collected. An ophthalmologic examination searching particularly for multifocal chorioretinitis was performed.
  
  
  RESULTS
  Of 64 patients who presented primarily with meningitis and/or encephalitis, 36 had IgM antibodies against WNV. The WNV-infected patients tended to be older (median age of 54 years vs 46 years in WNV infection and control groups, respectively) and more frequently had diabetes (30% vs 7% in WNV infection and control groups, respectively; P = .03). Multifocal chorioretinitis was found in 75% of WNV-infected patients but in no patient in the control group (P = .001). Blood glucose and amylase levels were higher in WNV-infected patients, whereas serum sodium levels were lower. The cerebrospinal fluid leukocyte count and protein levels were significantly higher in WNV meningitis or encephalitis. Overall, multifocal chorioretinitis had 100% specificity and 73% sensitivity (88% when only patients with meningitis or encephalitis were analyzed) for the diagnosis of WNV. Multivariate analysis disclosed multifocal chorioretinitis as the only predictor of WNV infection (odds ratio, 62; 95% confidence interval, 6-700; P = .001).
  
  
  CONCLUSIONS
  Multifocal chorioretinitis appears to be a specific marker of WNV infection, particularly in patients who present with meningoencephalitis. An ophthalmologic examination should be part of the routine evaluation of such patients.
authors.affiliation: Intensive Care Unit, CHU Fatouma Bourguiba, Monastir, Tunisia. f.abroug@rns.tn
authors.forename: Fekri
authors.initials: F
authors.lastname: Abroug
authors.forename: Lamia
authors.initials: L
authors.lastname: Ouanes-Besbes
authors.forename: Mondher
authors.initials: M
authors.lastname: Letaief
authors.forename: Foued
authors.initials: F
authors.lastname: Ben Romdhane
authors.forename: Moncef
authors.initials: M
authors.lastname: Khairallah
authors.forename: Henda
authors.initials: H
authors.lastname: Triki
authors.forename: Noureddine
authors.initials: N
authors.lastname: Bouzouiaia
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000276:immunology; D002825:Chorioretinitis / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D016000:Cluster Analysis; D004196:Disease Outbreaks; D004797:Enzyme-Linked Immunosorbent Assay; D015828:Eye Infections, Viral / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012720:Severity of Illness Index; D014416:Tunisia; D014901:West Nile Fever / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D014902:West Nile virus / Q000276:immunology
chemical_list: D000914:Antibodies, Viral