title: First reported chikungunya fever outbreak in the republic of Congo, 2011.
abstract: BACKGROUND
  Chikungunya is an Aedes -borne disease characterised by febrile arthralgia and responsible for massive outbreaks. We present a prospective clinical cohort study and a retrospective serological study relating to a CHIK outbreak, in the Republic of Congo in 2011.
  
  
  RESULTS
  We analysed 317 suspected cases, of which 308 (97.2%) lived in the city of Brazzaville (66.6% in the South area). Amongst them, 37 (11.7%) were CHIKV+ve patients (i.e., biologically confirmed by a real-time RT-PCR assay), of whom 36 (97.3%) had fever, 22 (66.7%) myalgia and 32 (86.5%) arthralgia. All tested negative for dengue. The distribution of incident cases within Brazzaville districts was compared with CHIKV seroprevalence before the outbreak (34.4% in 517 blood donors), providing evidence for previous circulation of CHIKV. We applied a CHIK clinical score to 126 patients recruited within the two first day of illness (including 28 CHIKV+ves (22.2%)) with sensitivity (78.6%) and specificity (72.4%) values comparing with those of the referent study in Reunion Island. The negative predictive value was high (92%), but the positive predictive value (45%) indicate poor potential contribution to medical practice to identify CHIKV+ve patients in low prevalence outbreaks. However, the score allowed a slightly more accurate follow-up of the evolution of the outbreak than the criterion "fever+arthralgia". The complete sequencing of a Congolase isolate (Brazza_MRS1) demonstrated belonging to the East/Central/South African lineage and was further used for producing a robust genome-scale CHIKV phylogenetic analysis.
  
  
  CONCLUSIONS
  We describe the first Chikungunya outbreak declared in the Republic of Congo. The seroprevalence study conducted amongst blood donors before outbreak provided evidence for previous CHIKV circulation. We suggest that a more systematic survey of the entomological situation and of arbovirus circulation is necessary in Central Africa for better understanding the environmental, microbiological and sociological determinants of emergence.
authors.affiliation: Aix Marseille University, IRD French Institute of Research for Development, EHESP French School of Public Health, EPV UMR_D 190 "Emergence des Pathologies Virales" 13005, Marseille, France.
authors.forename: Nanikaly
authors.initials: N
authors.lastname: Moyen
authors.affiliation: Aix Marseille University, IRD French Institute of Research for Development, EHESP French School of Public Health, EPV UMR_D 190 "Emergence des Pathologies Virales" 13005, Marseille, France.
authors.forename: Simon-Djamel
authors.initials: SD
authors.lastname: Thiberville
authors.affiliation: Aix Marseille University, IRD French Institute of Research for Development, EHESP French School of Public Health, EPV UMR_D 190 "Emergence des Pathologies Virales" 13005, Marseille, France.
authors.forename: Boris
authors.initials: B
authors.lastname: Pastorino
authors.affiliation: Aix Marseille University, IRD French Institute of Research for Development, EHESP French School of Public Health, EPV UMR_D 190 "Emergence des Pathologies Virales" 13005, Marseille, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Nougairede
authors.affiliation: Aix Marseille University, IRD French Institute of Research for Development, EHESP French School of Public Health, EPV UMR_D 190 "Emergence des Pathologies Virales" 13005, Marseille, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Thirion
authors.affiliation: Laboratoire National de Santé Publique, Brazzaville, Republic of Congo.
authors.forename: Jean-Vivien
authors.initials: JV
authors.lastname: Mombouli
authors.affiliation: Centre National de Transfusion Sanguine, Brazzaville, Republic of Congo.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Dimi
authors.affiliation: French National Reference Centre for Arboviruses, IRBA Armed Forces Biomedical Research Institute, 13013, Marseille, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Leparc-Goffart
authors.affiliation: Laboratory of Virology, National Institute for Infectious Diseases "L. Spallanzani", Via Portuense 292, 00149, Rome, Italy.
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Capobianchi
authors.affiliation: Centre National de Transfusion Sanguine, Brazzaville, Republic of Congo.
authors.forename: Amelia Dzia
authors.initials: AD
authors.lastname: Lepfoundzou
authors.affiliation: Aix Marseille University, IRD French Institute of Research for Development, EHESP French School of Public Health, EPV UMR_D 190 "Emergence des Pathologies Virales" 13005, Marseille, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: de Lamballerie
mesh_terms: D000293:Adolescent; D000328:Adult; D000330:Aedes; D000368:Aged; D000818:Animals; D065632:Chikungunya Fever / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D002646:Chikungunya virus / Q000235:genetics / Q000302:isolation & purification*; D003223:Congo / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D011446:Prospective Studies; D012189:Retrospective Studies; D016036:Seroepidemiologic Studies; D055815:Young Adult