Yellow fever outbreak potential in Djibouti, Somalia and Yemen: a mathematical modelling study
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Background
The importation of arbovirus diseases into new countries is a global concern. This risk is exacerbated by human movement and climate change effects. In the World Health Organization (WHO) Eastern Mediterranean regional office, three countries - Djibouti, Somalia, and Yemen - are currently classified as potential or moderate risk for yellow fever (YF) outbreaks.
Methods
Here we present a quantitative assessment of the risk of introduction and propagation of yellow fever virus (YFV) transmission in Djibouti, Somalia and Yemen. This modelling has two components: i) projecting the risk of importation of infectious individuals into the countries of interest using a radiation model of human movement and ii) estimating the risk of onward transmission given importation using a dynamic compartmental model of yellow fever virus transmission. Both components are multiplicatively combined to give an overall relative outbreak risk combining both risk of importation and risk of an outbreak given importation.
Results
We show that areas such as the western coast of Yemen, regions of Somalia bordering Ethiopia and Kenya, and Djibouti City have potential for YF outbreaks (where the estimated probability of an outbreak given an imported infectious case is over 50%). This is due to environmental suitability for transmission based on factors such as temperature and projected human mobility between endemic and at-risk regions.
Conclusions
Countries bordering existing YF endemic regions are potentially vulnerable to both introduction of YF cases and subsequent outbreak spread. This promotes the awareness of YF importation potential when conducting clinical surveillance in at-risk countries.
The importation of arbovirus diseases into new countries is a global concern. This risk is exacerbated by human movement and climate change effects. In the World Health Organization (WHO) Eastern Mediterranean regional office, three countries - Djibouti, Somalia, and Yemen - are currently classified as potential or moderate risk for yellow fever (YF) outbreaks.
Methods
Here we present a quantitative assessment of the risk of introduction and propagation of yellow fever virus (YFV) transmission in Djibouti, Somalia and Yemen. This modelling has two components: i) projecting the risk of importation of infectious individuals into the countries of interest using a radiation model of human movement and ii) estimating the risk of onward transmission given importation using a dynamic compartmental model of yellow fever virus transmission. Both components are multiplicatively combined to give an overall relative outbreak risk combining both risk of importation and risk of an outbreak given importation.
Results
We show that areas such as the western coast of Yemen, regions of Somalia bordering Ethiopia and Kenya, and Djibouti City have potential for YF outbreaks (where the estimated probability of an outbreak given an imported infectious case is over 50%). This is due to environmental suitability for transmission based on factors such as temperature and projected human mobility between endemic and at-risk regions.
Conclusions
Countries bordering existing YF endemic regions are potentially vulnerable to both introduction of YF cases and subsequent outbreak spread. This promotes the awareness of YF importation potential when conducting clinical surveillance in at-risk countries.
Date Issued
2026-12-01
Date Acceptance
2026-05-01
Citation
BMC Global and Public Health, 2026, 4 (1)
ISSN
2731-913X
Publisher
BMC
Journal / Book Title
BMC Global and Public Health
Volume
4
Issue
1
Copyright Statement
© The Author(s) 2026. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Identifier
10.1186/s44263-026-00284-9
Subjects
Yellow fever
Outbreak
Transmission risk
Mathematical modelling
Publication Status
Published
Article Number
ARTN 57
Date Publish Online
2026-06-08