INTRODUCTION
The Global Early Warning System for Health Threats and Emerging Risks at the Human-Animal Ecosystems Interface (GLEWS+) is a joint initiative of the Food and Agriculture Organization of the UN (FAO), the World Health Organization (WHO), and the World Organisation for Animal Health (WOAH).
Within this framework, the GLEWS+ Risk Assessment (RA) mechanism enables the three organizations to jointly assess emerging health threats at the human–animal–ecosystem interface and provide evidence-based risk estimates.
These assessments support Members and State Parties in strengthening the prevention, detection, response and control measures.
Event Description and Scope of the Assessment
Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic virus for which dromedary camels (Camelus dromedarius) are recognized as the primary animal reservoir.
Viral circulation within camel populations poses a risk of transmission to humans, particularly in settings characterized by frequent and close human–camel interactions.
Historically, MERS-CoV strains detected in dromedary camels in Africa have belonged to clade C, whereas clade B viruses have been associated with the majority of reported human MERS cases and have predominantly circulated in dromedary camel populations in the Middle East.
The recent detection of MERS-CoV clade B genome fragments in camels from the Nile Basin region represents a notable epidemiological development, suggesting the possibility of inter-regional viral movement and genetic mixing.
This finding may have implications for virus circulation and transmission dynamics, including potential changes in the risk of zoonotic spillover to humans and/or alterations in viral transmissibility and pathogenicity.
This assessment evaluates the risk of spread of MERS-CoV clade B within camel populations at both sub-regional (Nile Basin) and regional (Africa) levels.
It also assesses the risk of spillover from infected camels to humans in Nile Basin countries.
The assessment considers available virological, epidemiological, ecological, and socio-economic factors that influence virus circulation, including camel husbandry practices, pastoralist mobility patterns, cross-border animal movements, live-animal trade networks, and the extent of human-camel contact in the region.
Information used in this assessment was compiled from eight countries in Africa reporting camel populations exceeding 10,000 in 2024.
The countries included in the assessment are:
° Chad,
° Egypt*,
° Eritrea*,
° Ethiopia*,
° Kenya*,
° Libya,
° South Sudan* and
° Sudan*.
The six countries belonging to the Nile Basin sub-region are indicated by an asterisk (*).
This risk assessment reflects information available to 27 July 2026. FAO, WHO and WOAH will review and update the assessment as new information becomes available.
SUMMARY
Middle East respiratory syndrome coronavirus (MERS-CoV) is an enveloped, positive-sense RNA virus belonging to the genus Betacoronavirus.
It causes Middle East respiratory syndrome (MERS), a zoonotic respiratory disease first recognized in 2012, following the detection of human cases in Saudi Arabia and Jordan.
As of 11 June 2026, a total of 2,637 laboratory-confirmed human cases have been reported to WHO globally, the majority from countries in the Arabian Peninsula, with an estimated crude case fatality ratio (CFR) of approximately 37%. (WHO, 2025c)
Dromedary camels (Camelus dromedarius) are the primary animal reservoir of MERS-CoV and the main source of zoonotic transmission to humans.
Human infections are thought to occur through direct or indirect contact with infected camels.
Consumption of raw camel products is considered a plausible route of exposure, although it has not been definitively confirmed as a primary transmission pathway.
Human-to-human transmission can occur, particularly in healthcare settings and among those in close-contact.
MERS-CoV antibodies have been found in other camelid species, including Bactrian camels, hybrid camels, llamas and alpacas, indicating susceptibility to infection (Islam, 2003).
However, these species are not considered to play a significant role in the current epidemiology of MERS.
MERS-CoV has evolved into three genetic clades (A, B, and C) with distinct geographic patterns.
Clade B predominates in the Arabian Peninsula and has been associated with all recent human infections.
Clade A has not been detected since 2015 and is considered extinct.
Clade C circulates among dromedary camels across Africa and despite frequent camel imports from Nile Basin countries into the Arabian Peninsula, has not become established in local camel populations.
Experimental and phenotypic studies indicate that clade B viruses exhibit higher replication efficiency in human respiratory tissues and experimentally infected camelids, more efficient cellular entry, and prolonged viral shedding compared with clade C viruses. (Rodon, 2023)
These characteristics suggest a greater zoonotic potential and an increased likelihood of transmission to humans. (Zhou, 2021)
The global camel population is estimated at over 42 million heads as of 2023, with more than 80% of the population in Africa (FAO, 2025a).
Camel trade within Africa is predominantly regional and fragmented, with significant informal cross-border movement. (WHO, 2025d, FAO, 2026) In the Nile Basin and the Horn of Africa {1}.
Camel trade and movement are largely driven by informal cross-border pastoralist systems, with frequent but poorly documented movements between neighboring countries such as Sudan, Ethiopia, Kenya, and South Sudan.
Sudan plays a central role as a major camel exporter, with substantial formal and informal movements to neighboring countries and toward North Africa, while Egypt functions primarily as a terminal hub where camels from multiple origins converge for trade and slaughter.
In contrast, long-distance east-to-west transcontinental movement appears limited, with little evidence of sustained camel movement from the Nile Basin into North or West Africa. (Younan et al., 2016)
Recent genomic surveillance studies have suggested the introduction of MERS-CoV clade B strains into camel populations in the Nile Basin, outside its historically recognized circulation in the Arabian Peninsula.
In Egypt, phylogenetic analyses of a camel-derived sample identified genome fragments clustering with clade B viruses from the Arabian Peninsula, circulating alongside endemic African clade C viruses (Gomaa, Edwards, Wang, Taweel, et al., 2025).
Recombination analyses in these studies were interpreted by the authors as suggesting potential genomic mixing between introduced clade B and endemic clade C lineages, highlighting a potential for inter-regional viral exchange and the emergence of novel variants.
However, as the publicly available sequences are incomplete, these findings require confirmation through full genome sequencing.
In a separate study (Hassan et al., 2025), metagenomic sequencing of nasal swabs from camels imported from Sudan also detected MERS-CoV genome fragments clustering with clade B human and camel strains.
Whole genome sequencing would be necessary to confirm these findings and better characterize their evolutionary relationships.
Overall, while these observations suggest the possible introduction of clade B viruses into camel population in the Nile Basin sub-region, additional research is required to determine whether there is sustained circulation, establishment, or recombination of clade B viruses in continental African camel populations.
Using a qualitative evidence-based approach and considering the assessed likelihood and consequences in the countries assessed, the overall risk at sub-regional level (Nile Basin) of further introduction and spread of MERS-CoV clade B within camel populations is minor.
The risk of introduction and spread from camel populations in the Nile Basin to camel populations in neighbouring countries is also assessed as minor.
However, if MERS-CoV clade B is introduced and established in camel populations in the Nile Basin countries, the public health risk of spillover from camels to humans exposed to infected camels or their products is assessed as high.
The level of confidence in the risk estimates is considered low for the first two questions, reflecting limitations in the quality and completeness of available genomic data, the presence of plausible but unconfirmed transmission pathways, very limited surveillance in camels and humans, and evolving camel trade dynamics that may facilitate virus spread within and beyond the Nile Basin.
The level of confidence is considered moderate for the third question.
While the clinical presentation and potential consequences of MERS-CoV infection in humans are well documented and observed in previous outbreaks, important uncertainties remain regarding the social, behavioral, and contextual factors that influence the likelihood of camel- to- human spillover in the Nile Basin.
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{1} Countries in the Horn of Africa are: Djibouti, Eritrea, Ethiopia, and Somalia
Source:
Link: https://www.who.int/publications/m/item/risk-assessment-of-the-introduction--spread--and-zoonotic-spillover-of-mers-cov-clade-b-in-camel-populations-of-the-nile-basin-and-across-africa
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