Passive Facility-based fever surveillance for Dengue at the time of Chikungunya introduction in Colombia

Background: The global burden of arboviruses has increased lately and while dengue has been endemic in Colombia, chikungunya was recently introduced in 2014. Methods & Materials: A passive facility-based fever surveillance study was conducted to estimate the age-specific incidence of symptomatic dengue cases and characterize its clinical profile in Colombia. Individuals with undifferentiated fever (<7 days), between 1-55 years, were followed-up for 28 days. Rapid diagnostic tests, serological and molecular analyses were done in paired samples to identify dengue and circulating serotypes. Underreport was assessed and age-specific multiplication factors were calculated. Results: From 839 febrile participants, 686 completed the study. There were 295 (33.2%) confirmed dengue infections (57.3% primary infections), and 191 (22.8%) chikungunya cases. Dengue cases were younger (median = 18 years; IQR = 12-29) than chikungunya cases (median = 25 years; IQR = 16-38). Presence of thrombocytopenia (OR:2.2; 95%CI = 1.3-3.8) and abdominal pain (OR:1.9; 95%CI = 1.3-3.0) were predictors of dengue, and the presence of rash (OR: 9.9; 95%CI = 5.3- 18.6) was the main predictor of chikungunya. All four DENV serotypes were circulating in the study area with DENV1 as the most prevalent 47%. Conclusion: This study highlights that despite the important level of underreporting, dengue is still an important cause of fever among all age groups in this setting. Moreover, dengue and chikungunya are present in Colombia and this study contributes to the evidence of their simultaneous ongoing transmission.