Transmission Dynamics of Mpox in Sierra Leone: Evidence of Symptomatic and Pre-symptomatic Transmission

Authors

  • Abdulai Alpha Jalloh Directorate of Planning, Police and Research, National Public Health Agency, Free town, Sierra Leone
  • Mohamed Boie Jalloh Directorate of Planning, Policy and Research, National Public Health Agency, Free town, Sierra Leone
  • James Sylvester Squire Directorate of Surveillance and Epidemiology, National Public Health Agency, Free town Sierra Leone
  • Ibrahim Kamara Department of Emergency, Preparedness and Response World Health Organization, Freetown, Sierra Leone
  • Victor Caulker Department of Emergency, Preparedness and Response World Health Organization, Freetown, Sierra Leone
  • George Ameh World Health Organization, Freetown, Sierra Leone
  • Alhaji U. N'jai University of Sierra Leone, Freetown, Sierra Leone, and Koinadugu College, Kabala, Sierra Leone, and California University of Science and Medicine, Colton, California
  • Mohamed Alex Vandi National Public Health Agency, Free town, Sierra Leone
  • Foday Sahr National Public Health Agency, Free town, Sierra Leone

DOI:

https://doi.org/10.4314.3.6

Abstract

Background:
Understanding transmission dynamics of mpox in low-resource settings remains limited, particularly in the context of evolving outbreaks in Africa. This study aimed to characterize exposure patterns, transmission pathways, and timing of infection among mpox cases in Sierra Leone.

Methods:
A retrospective, case-ascertained transmission study was conducted among confirmed mpox cases. Data were collected through field investigations and complemented with surveillance data from the District Health Information System (DHIS2). Exposure characteristics, type of interaction, and symptomatic status of the source case at the time of contact were analyzed. Transmission timing was classified as pre-symptomatic, symptomatic, or unknown. Associations between exposure type and transmission timing were assessed using Fisher’s exact test.

Results:
A total of 201 mpox cases were included in the analysis. Among cases with available exposure data, 29% reported contact with a symptomatic individual, while 49% reported no known contact and 21% were unknown. Direct physical non-sexual contact (44%) and sexual contact (32%) were the most common exposure types. Most transmission events occurred during the symptomatic phase (66%), while 17% occurred during the pre-symptomatic phase and 17% were unknown. A statistically significant association was observed between exposure type and transmission timing (p = 0.010), indicating that the nature of contact may influence when transmission occurs.

Conclusion:
Mpox transmission in Sierra Leone was primarily driven by close interpersonal contact, with evidence of both symptomatic and pre-symptomatic transmission. These findings highlight the need for strengthened contact tracing and early intervention strategies that extend beyond symptom-based detection.

Keywords: exposure characteristics, mpox, Sierra Leone, symptomatic, transmission dynamic,

 

 

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Published

2026-06-12

Issue

Vol. 16 No. 3 (2026): May 2026

Section

Original Articles

License

Submission of manuscripts to the Sierra Leone Journal of Biomedical Research is of the understanding that the article either in part or whole is not under consideration for publication in any other Journal. Accepted papers become the permanent property of Sierra Leone Journal of Biomedical Research but unrestricted use, distribution, and reproduction in any medium is permitted, provided the original work is properly cited.