Risk factors associated with dengue and chikungunya seroprevalence and seroconversion among urban populations in western and coastal Kenya.

backgroundDengue virus (DENV) and chikungunya virus (CHIKV) are arboviruses that are endemic to Kenya. Most DENV infections are asymptomatic resulting in underreporting of cases and symptomatic cases are often misdiagnosed as malaria. Past studies focusing on arboviruses in Kenya are mostly limited to outbreak periods, leaving a gap in knowledge about inter-epidemic arboviral prevalence and associated risk factors. In this study, we aim to determine the risk factors for seroprevalence of and seroconversion to DENV and CHIKV among urban populations in two sites in Kenya. METHODOLOGY/PRINCIPAL

findingsIn this prospective cohort study, 4,529 participants were recruited by household from two urban sites in Kenya: Kisumu in the west and Ukunda in the coast. Participants were followed from December 2019 until February 2022 at 6-month intervals. Questionnaire data and blood samples were collected for demographic and serologic data, respectively. If a participant had a febrile illness during the study, they were registered for a sick visit, treated and blood samples were taken to test for acute DENV or CHIKV infection by RT-PCR. Our results showed a 22.8% (1,033/4529) seropositivity rate for DENV and a 21.4% (969/4,529) seropositivity rate for CHIKV; 9% (409/4529) were found to be seropositive for both. DENV and CHIKV seropositivity was more common on the coast (43.9% vs. 6% with p < 0.01for DENV, 22.6% vs. 20.5% with p = 0.09 for CHIKV) than in the west and among adults than children (30.8% vs 11.5% with p < 0.01 for DENV, 32.4% vs 5.9% with p < 0.01 for CHIKV). Of the total participants, 4% (183/4529) and 3% (136/4529) seroconverted for DENV and CHIKV, respectively, during the 2-year study period. In our multivariate analysis, controlling for variables in a stepwise selection, being from the coastal site and of older age were the main risk factors for DENV seropositivity while being from the coastal site, having greater levels of education, and crowding in the household were significant risk factors for CHIKV seropositivity. In those participants who were newly exposed to these viruses during the study period, being from the coastal site, high socioeconomic status (SES), and not having window screens in the household were the significant risk factors for both DENV and CHIKV seroconversion. CONCLUSIONS/SIGNIFICANCE: Our results show significant DENV and CHIKV seropositivity among adults and children in urban western and coastal Kenya and evidence of active circulation of both DENV and CHIKV between 2019 and 2022. There were higher rates of seropositivity and active circulation on the coast where past outbreaks have occurred. Although lower education and socioeconomic status (SES) were reported as risk factors for arboviral infections in the past, we found more risk of seropositivity among individuals with higher SES and education, demonstrating the community-wide risk of seropositivity in urban settings. Our findings highlight the need for active surveillance of arboviruses and interventions in Kenya, especially on the coast.