High seroprevalence of antibodies to Dengue, Chikungunya, and Zika viruses in Dire Dawa, Ethiopia: A cross-sectional survey in 2024.

BACKGROUND

Aedes-borne diseases infect millions of people each year. In the last decade several arbovirus outbreaks have been reported in Ethiopia. Arbovirus diagnosis and surveillance is lacking, and the true burden is unknown.

METHODS

In this study we conducted a seroprevalence survey using a commercially available test kit that tests for immunological responses to IgM and IgG for dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV) viruses in Dire Dawa city, eastern Ethiopia. A total of 339 individuals were sampled using a household-based clustered design. As a contextual comparison, a secondary survey was conducted among 180 individuals in Addis Ababa, where no Aedes-borne virus outbreaks have been reported.

FINDINGS

We found a high IgG seroprevalence for DENV (76%), CHIKV (44%), and ZIKV (38%), and <20% IgM seropositivity across all viruses. In contrast, minimal seropositivity was detected in Addis Ababa (where the highest seropositivity we found was to IgM for DENV at approximately 3%.) Age-specific trends showed early and widespread DENV exposure, with over half of the population seropositive by age 10. Quantitative antibody levels indicated strong correlation between DENV and ZIKV IgG, suggesting potential cross-reactivity. However, higher DENV IgG titers among ZIKV-positive individuals raise the possibility of true prior co-exposure. Intraclass correlation analyses revealed household-level clustering for DENV and CHIKV responses but not for ZIKV.

CONCLUSIONS

These results suggest intense and possibly ongoing transmission of Aedes-borne viruses in Dire Dawa, particularly dengue and chikungunya. Apparent ZIKV exposure warrants cautious interpretation given the potential for cross-reactivity, but cannot be ruled out. Our findings underscore the need for improved arbovirus surveillance and diagnostic capacity in Ethiopia, especially in urban centers where competent vectors are established.