title: Seroepidemiology of dengue in travellers: a paired sera analysis.
abstract: BACKGROUND
  Dengue is a frequent cause of fever in travellers. The true extent is unknown as many infections are asymptomatic or undiagnosed.
  
  
  METHODS
  We used paired sera, with pre- and post-travel specimens from Swiss travellers to tropical destinations, to evaluate the seroepidemiology of travel-related dengue. Post-travel specimens were tested for the presence of IgG and IgM antibodies to dengue antigen serotypes (1, 2, 3 and 4) using an indirect enzyme-linked immunosorbent assay (ELISA). All post-travel sera that screened as positive for dengue IgG or IgM antibodies were re-tested with the corresponding pre-travel sera as paired assays in order to detect seroconversion.
  
  
  RESULTS
  There were 285 travellers with specimens available for analysis. Two hundred and fifty seven of the 285 individuals (90.2%) had negative dengue serology post-travel. Of the remaining 28 cases, 25 were dengue IgG positive and 3 had equivocal results. This corresponds to IgG seropositivity in 8.9%. Eighteen of these 25 individuals had a pre-travel specimen available for testing, of which 15 were positive for IgG consistent with possible past exposure. Three of the 18 had negative serology pre-travel, indicating possible recent infection. This corresponds to an attack rate of possible dengue of 1.1% and an incidence rate of 6.7 per 1000 person-months (95% CI 0-60.0). Two of these three individuals had received yellow fever vaccine for their trip, raising the potential of cross-reactivity. The confirmed dengue attack rate therefore was 0.23% with a corresponding incidence rate of 2.2 per 1000 person-months (95% CI-0-33.1).
  
  
  CONCLUSIONS
  Seroepidemiology provides additional evidence of an appreciable risk of acute dengue infection among travellers to tropical destinations.
authors.affiliation: Department of Epidemiology and Preventive Medicine, Monash University, Australia. karin.leder@monash.edu
authors.forename: Karin
authors.initials: K
authors.lastname: Leder
authors.forename: Margot
authors.initials: M
authors.lastname: Mutsch
authors.forename: Patricia
authors.initials: P
authors.lastname: Schlagenhauf
authors.forename: Christine
authors.initials: C
authors.lastname: Luxemburger
authors.forename: Joseph
authors.initials: J
authors.lastname: Torresi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood*; D015331:Cohort Studies; D003715:Dengue / Q000453:epidemiology* / Q000276:immunology; D003716:Dengue Virus / Q000276:immunology* / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012306:Risk; D016036:Seroepidemiologic Studies; D013557:Switzerland / Q000453:epidemiology; D014195:Travel; D014611:Vaccination; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M
keywords: Dengue; ELISA; Seroepidemiology; Traveller