Prevalence of Dengue and Chikungunya in the Horn of Africa: A Systematic Review and Meta-analysis

Background: Dengue virus (DENV) and Chikungunya virus (CHIKV) are important mosquito-borne arboviruses with expanding global distributions. Although recurrent outbreaks have occurred in the Horn of Africa since the early 2000s, their epidemiology and burden remain poorly characterized. This systematic review and meta-analysis estimated the prevalence of DENV and CHIKV, their distribution by country, diagnostic methods, circulating DENV serotypes, and mosquito vectors. Methods: Following PRISMA guidelines, PubMed, Web of Science, Scopus, SpringerLink, Nature Portfolio, and Google Scholar were searched for studies published up to October 2025. Eligible studies reported DENV and/or CHIKV infections in humans or mosquitoes in Kenya, Ethiopia, or Somalia. Random-effects meta-analyses were performed, with subgroup analyses by country, population, setting, and diagnostic method. Results: Of 3,351 records, 65 studies met the inclusion criteria, most from Kenya (63.1%), followed by Ethiopia (30.8%) and Somalia (6.1%). Pooled DENV prevalence was 20% for IgG, 10% for IgM, 6% for NS1, and 4% by PCR. Corresponding CHIKV prevalence was 5% for IgG, 8% for IgM, and 4% by PCR. Significant differences between countries were observed for DENV NS1 (p<0.0001) and PCR-confirmed infections (p=0.01). DENV prevalence was highest in the general population (16%) compared with febrile patients (6%) and mosquito vectors (1%) (p=0.033), whereas CHIKV prevalence was highest in rural settings (15%) (p=0.0002). All four DENV serotypes circulated in Kenya and Ethiopia, while DENV-2 and DENV-3 were reported in Somalia. Aedes aegypti was the predominant vector, reported in 92.3% of vector studies. Conclusions: DENV and CHIKV are important and likely underrecognized arboviral threats to global public health and in the Horn of Africa, with evidence of ongoing transmission and widespread exposure. Strengthened surveillance, diagnostic capacity, vector control, and regional collaboration are needed to mitigate their growing public health impact.