title: High rates of o'nyong nyong and Chikungunya virus transmission in coastal Kenya.
abstract: BACKGROUND
  Chikungunya virus (CHIKV) and o'nyong nyong virus (ONNV) are mosquito-borne alphaviruses endemic in East Africa that cause acute febrile illness and arthritis. The objectives of this study were to measure the seroprevalence of CHIKV and ONNV in coastal Kenya and link it to demographics and other risk factors.
  
  
  METHODS
  Demographic and exposure questionnaires were administered to 1,848 participants recruited from two village clusters (Milalani-Nganja and Vuga) in 2009. Sera were tested for alphavirus exposure using standardized CHIKV IgG ELISA protocols and confirmed with plaque reduction neutralization tests (PRNT). Logistic regression models were used to determine the variables associated with seropositivity. Weighted K test for global clustering of houses with alphavirus positive participants was performed for distance ranges of 50-1,000 meters, and G* statistic and kernel density mapping were used to identify locations of higher seroprevalence.
  
  
  RESULTS
  486 (26%) participants were seropositive by IgG ELISA. Of 443 PRNT confirmed positives, 25 samples (6%) were CHIKV+, 250 samples (56%) were ONNV+, and 168 samples (38%) had high titers for both. Age was significantly associated with seropositivity (OR 1.01 per year, 95% C.I. 1.00-1.01); however, younger adults were more likely to be seropositive than older adults. Males were less likely to be seropositive (p<0.05; OR 0.79, 95% C.I. 0.64-0.97). Adults who owned a bicycle (p<0.05; OR 1.37, 95% C.I. 1.00-1.85) or motor vehicle (p<0.05; OR 4.64, 95% C.I. 1.19-18.05) were more likely to be seropositive. Spatial analysis demonstrated hotspots of transmission within each village and clustering among local households in Milalani-Nganja, peaking at the 200-500m range.
  
  
  CONCLUSIONS
  Alphavirus exposure, particularly ONNV exposure, is common in coastal Kenya with ongoing interepidemic transmission of both ONNV and CHIKV. Women and adults were more likely to be seropositive. Household location may be a defining factor for the ecology of alphaviral transmission in this region.
authors: Children's Hospital Oakland Research Institute, Oakland, California, United States of America; Case Western Reserve University, Cleveland, Ohio, United States of America.
authors: A Desiree
authors: AD
authors: LaBeaud
authors: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
authors: Tamara
authors: T
authors: Banda
authors: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
authors: Julie
authors: J
authors: Brichard
authors: Division of Vector Borne and Neglected Tropical Diseases, Ministry of Health, Msambweni, Kenya.
authors: Eric M
authors: EM
authors: Muchiri
authors: Case Western Reserve University, Cleveland, Ohio, United States of America.
authors: Peter L
authors: PL
authors: Mungai
authors: Technical University of Mombasa, Mombasa, Kenya.
authors: Francis M
authors: FM
authors: Mutuku
authors: CDC, Fort Collins, Colorado, United States of America.
authors: Erin
authors: E
authors: Borland
authors: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
authors: Ginny
authors: G
authors: Gildengorin
authors: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
authors: Sarah
authors: S
authors: Pfeil
authors: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
authors: Crystal Y
authors: CY
authors: Teng
authors: University of NC, Chapel Hill, North Carolina, United States of America.
authors: Kristin
authors: K
authors: Long
authors: University of NC, Chapel Hill, North Carolina, United States of America.
authors: Mark
authors: M
authors: Heise
authors: CDC, Fort Collins, Colorado, United States of America.
authors: Ann M
authors: AM
authors: Powers
authors: Emory University, Atlanta, Georgia, United Statas of America.
authors: Uriel
authors: U
authors: Kitron
authors: Case Western Reserve University, Cleveland, Ohio, United States of America.
authors: Charles H
authors: CH
authors: King
mesh_terms: D000328:Adult; D000351:Africa, Eastern; D000368:Aged; D018354:Alphavirus Infections / Q000453:epidemiology* / Q000635:transmission; D000818:Animals; D065632:Chikungunya Fever / Q000453:epidemiology* / Q000635:transmission; D002646:Chikungunya virus / Q000276:immunology*; D002648:Child; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000821:virology; D007630:Kenya / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D064202:O'nyong-nyong Virus / Q000276:immunology*; D016036:Seroepidemiologic Studies; D011795:Surveys and Questionnaires