{Summary}
Risk statement
This rapid risk assessment was triggered by the recent increase in yellow fever activity in a limited number of countries in West and Central Africa, within the broader group of countries classified as high risk for yellow fever in the WHO African Region.
It focuses primarily on the evolving situations in Burkina Faso, Cameroon, Côte d’Ivoire, Ghana and Liberia, while considering relevant developments in other affected countries where necessary.
It assesses the public health risk associated with ongoing yellow fever transmission in the WHO African Region during 2026, considering the impact on human health, the potential for geographical spread, including cross-border spread, and the risk of insufficient control capacity.
It builds on the Global Rapid Risk Assessment for yellow fever that was finalized on 5 June 2026 and incorporates regional information available up to 12 October 2026.
Between 1 January and 12 October 2026, 67 confirmed cases including 18 deaths were recorded in nine countries in the WHO African Region.
However, the most recent cases were concentrated in Burkina Faso, Côte d’Ivoire, Ghana and Liberia, particularly in districts near international borders.
Differences in reporting cut-off dates and case classifications across available sources affect the comparability of regional epidemiological data.
The likelihood of continued transmission and additional human cases is considered likely. Several affected districts have previously identified immunity gaps, including areas where preventive vaccination has not been implemented or where population immunity remains insufficient despite past vaccination activities.
Unvaccinated and under-vaccinated populations remain at highest risk, particularly among rural and forestedge communities, mobile and cross-border populations, and people with occupational exposure in forested, agricultural and mining environments.
The concentration of outbreaks in border areas increases the potential for further geographical spread.
Population mobility, frequent crossborder movement, trade, agricultural activities, pastoral movements and mining operations may facilitate transmission between affected and neighbouring countries.
Introduction into densely populated urban or peri-urban areas with established Aedes aegypti populations and low population immunity could result in larger outbreaks and place additional pressure on response capacities.
Environmental and seasonal factors, including rainfall, temperature and vector abundance, may influence transmission dynamics. Evolving El Niño conditions may further modify the environmental and operational context but should not be considered a direct cause of the outbreaks.
The region has important capacities, including established surveillance systems, a regional laboratory network, routine and reactive vaccination mechanisms, outbreak-response experience, access to the international emergency vaccine stockpile and activated response structures.
However, persistent immunity gaps, surveillance and laboratory challenges, delays in specimen referral and confirmation, insecurity, access constraints, operational challenges to reach unprotected at-risk communities, funding constraints and competing public health emergencies continue to affect timely detection, investigation, and control.
The simultaneous occurrence of outbreaks and epidemic signals in multiple countries increases demand for laboratory confirmation, vaccination activities, outbreak investigations and cross-border coordination.
Based on the likelihood of continued transmission, the risk of cross-border spread, documented immunity gaps and operational constraints affecting outbreak control, the overall public health risk is assessed as moderate in the WHO African Region, with moderate confidence.
The global risk remains low, with high confidence, as transmission remains concentrated in areas with a history of yellow fever circulation and established international response mechanisms remain available.
Confidence in the regional assessment is moderate because reporting cut- off dates and case classifications vary across available sources, some laboratory results remain pending, entomological information is limited, and cases may be under detected in remote or insecure areas.
Confidence is high regarding the hazard and established transmission routes, but lower for the magnitude and geographical extent of current transmission because of differences in national reporting cut-offs and case classifications, pending confirmatory testing, incomplete reconciliation of line lists and laboratory results, limited entomological information, and possible under- detection in remote or insecure areas.
The assessment will be updated as new epidemiological, laboratory and operational information becomes available
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Source: World Health Organization, https://www.who.int/publications/m/item/who-rapid-risk-assessment--yellow-fever--who-african-region-v.1
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