title: Population seroprevalence study after a West Nile virus lineage 2 epidemic, Greece, 2010.
abstract: BACKGROUND
  During summer 2010, 262 human cases including 35 deaths from West Nile virus (WNV) infection were reported from Central Macedonia, Greece. Evidence from mosquitoes, birds and blood donors demonstrated that the epidemic was caused by WNV lineage 2, which until recently was considered of low virulence. We conducted a household seroprevalence study to estimate the spread of infection in the population during the epidemic, ascertain the relationship of infection to clinical disease, and identify risk factors for infection.
  
  
  METHODS
  We used a two-stage cluster design to select a random sample of residents aged ≥18 years in the outbreak epicentre. We collected demographic, medical, and risk factor data using standard questionnaires and environmental checklists, and tested serum samples for presence of WNV IgG and IgM antibodies using ELISA.
  
  
  RESULTS
  Overall, 723 individuals participated in the study, and 644 blood samples were available. Weighted seropositivity for IgG antibodies was 5.8% (95% CI: 3.8-8.6; n=41). We estimated that about 1 in 130 (1:141 to 1:124) infected individuals developed WNV neuroinvasive disease, and approximately 18% had clinical manifestations attributable to their infection. Risk factors for infection reflected high exposure to mosquitoes; rural residents were particularly at risk (prevalence ratio: 8.2, 95% CI: 1.1-58.7).
  
  
  CONCLUSIONS
  This study adds to the evidence that WNV lineage 2 strains can cause significant illness, demonstrating ratios of infection to clinical disease similar to those found previously for WNV lineage 1.
authors.affiliation: European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden ; Dutch National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Georgia A F
authors.initials: GA
authors.lastname: Ladbury
authors.forename: Magda
authors.initials: M
authors.lastname: Gavana
authors.forename: Kostas
authors.initials: K
authors.lastname: Danis
authors.forename: Anna
authors.initials: A
authors.lastname: Papa
authors.forename: Dimitris
authors.initials: D
authors.lastname: Papamichail
authors.forename: Spiros
authors.initials: S
authors.lastname: Mourelatos
authors.forename: Sandra
authors.initials: S
authors.lastname: Gewehr
authors.forename: George
authors.initials: G
authors.lastname: Theocharopoulos
authors.forename: Stefanos
authors.initials: S
authors.lastname: Bonovas
authors.forename: Alexis
authors.initials: A
authors.lastname: Benos
authors.forename: Takis
authors.initials: T
authors.lastname: Panagiotopoulos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D058872:Epidemics; D005260:Female; D006115:Greece / Q000453:epidemiology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012306:Risk; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D014901:West Nile Fever / Q000097:blood* / Q000453:epidemiology / Q000276:immunology*; D014902:West Nile virus / Q000276:immunology*; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G