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

## TL;DR

A study in Dire Dawa, Ethiopia, found high past exposure to dengue, chikungunya, and possibly Zika viruses, highlighting the need for better surveillance in urban areas.

## Contribution

The study provides the first detailed seroprevalence data for Aedes-borne viruses in Dire Dawa, revealing high exposure and household clustering.

## Key findings

- High IgG seroprevalence for dengue (76%), chikungunya (44%), and Zika (38%) was observed in Dire Dawa.
- DENV and ZIKV IgG levels showed strong correlation, suggesting cross-reactivity or co-exposure.
- Household clustering was found for DENV and CHIKV but not ZIKV, indicating localized transmission patterns.

## Abstract

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.

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.

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.

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.

Mosquito-borne viruses such as dengue, chikungunya, and Zika pose growing public health challenges in many parts of Africa, but limited surveillance makes it difficult to assess their true burden. We conducted a serosurvey in Dire Dawa, a city in eastern Ethiopia that has experienced outbreaks of dengue and chikungunya. Blood samples from 339 individuals were tested for antibodies to dengue, chikungunya, and Zika viruses. We found high levels of prior exposure to dengue (76%) and chikungunya (44%), and observed apparent Zika virus antibodies in 38% of participants. Since antibodies can cross-react between related viruses, we interpret the Zika findings with caution and consider them hypothesis-generating. In contrast, we found low evidence of exposure in a separate sample from Addis Ababa, a city with no known history of arbovirus outbreaks. These results highlight the importance of community-based serosurveillance for detecting overlooked transmission and guiding targeted prevention strategies in urban African settings.