A disease that drew little international attention when it was first isolated nearly 70 years ago in what is now the Democratic Republic of the Congo is quietly circulating across the country’s vast and ecologically diverse terrain — and until now, almost no one was systematically looking for it. Crimean-Congo hemorrhagic fever (CCHF), caused by a tickborne virus capable of killing up to 40 percent of infected patients in clinical settings, has long been a known but poorly characterized threat in Central Africa. A new seroprevalence study spanning 25 of the DRC’s 26 provinces is beginning to fill that gap, with findings that carry serious implications for regional outbreak preparedness and transboundary biosecurity.
Published in the April 2026 issue of Emerging Infectious Diseases, the study — led by Boniface Pongombo Lombe and colleagues from the Central Veterinary Laboratory of Kinshasa, the Institut National de Recherche Biomédicale, the University of Kinshasa, Hokkaido University, and other institutions — represents the most geographically comprehensive investigation of CCHF virus (CCHFV) seroprevalence ever conducted in the DRC. The researchers found that approximately 4.4 percent of human samples tested positive for CCHFV-specific antibodies, and nearly 29 percent of domestic ruminants showed evidence of prior infection — a striking figure that signals widespread, sustained viral circulation in the country’s livestock population.
The research team conducted a retrospective cross-sectional serosurvey using archived human and animal serum samples collected between 2017 and 2019. Human samples — 1,239 in total — were drawn from a national yellow fever surveillance system, specifically from patients who had presented with febrile illness and tested negative for yellow fever virus. Animal samples totaled 1,114 and were collected from cattle, goats, and sheep across markets and farms in 10 provinces. All samples were tested using an in-house nucleoprotein-based ELISA designed to detect CCHFV-specific IgG antibodies. The study’s geographic reach covered three major climate zones and four distinct vegetation types, allowing the team to examine ecological correlates of seropositivity across both human and animal populations.
Cattle as Sentinels, Mountains as Hotspots
Among domestic animals, cattle emerged as the clearest epidemiological signal. Cattle seroprevalence reached 42.8 percent — nearly nine times higher than for other species tested — consistent with cattle’s role as preferred hosts for Hyalomma ticks, the principal vectors of CCHFV. Goats showed a seroprevalence of 5.3 percent, while sheep came in at just 2.0 percent. Seroprevalence among animals rose with age, and female animals — kept longer for breeding and milk production — were more likely to test positive than males, reflecting longer cumulative exposure to tick bites.
In humans, age was similarly associated with seropositivity. Adults aged 20 to 29 years and those over 50 were each approximately three times more likely to test positive than younger groups, a pattern the authors attribute to cumulative tick exposure over a lifetime. Geographically, the data point strongly toward the country’s eastern highland regions as high-risk zones. Samples from locations with tropical monsoon climates, grassy or mountain savanna vegetation, and elevations between 600 and 800 meters above sea level all showed elevated odds of seropositivity. The provinces of Ituri, Nord Kivu, and Sud Kivu — part of the African Great Lakes region and major corridors for cross-border cattle trade — recorded among the highest prevalences observed in both humans and animals.
The team also specifically tested for cross-reactivity with Nairobi sheep disease virus, a serologically related orthonairovirus also present in the region. Although some cross-reactivity was observed, antibody reactivity values were consistently higher against CCHFV antigens than against the comparator virus, lending confidence to the specificity of the findings.
Looking Forward
The eastern DRC sits at a geopolitical and ecological crossroads: the Great Lakes region’s cross-border cattle trade creates conditions for the movement of Hyalomma ticks — and the pathogens they carry — across national boundaries into Rwanda, Uganda, Burundi, and beyond. Uganda, notably, has reported CCHFV animal seroprevalence exceeding 74 percent in some surveys, suggesting that the high-risk zone is contiguous and transnational in scope.
From a biosecurity standpoint, the DRC’s history of hemorrhagic fever outbreaks — some with unidentified causative agents — makes systematic CCHFV surveillance a preparedness imperative. The study’s authors highlight a particularly practical finding: the yellow fever surveillance infrastructure already in place across the DRC can function as a dual-purpose platform, simultaneously capturing epidemiological signals for CCHF. Leveraging existing systems in this way would reduce the cost and logistical burden of CCHFV monitoring without requiring the construction of parallel surveillance networks.
Rising temperatures and shifting precipitation patterns are expected to expand suitable Hyalomma habitat into areas not currently considered endemic, potentially driving CCHFV into new human and animal populations across Africa and beyond. The virus has already surfaced in human cases and tick populations in southern Europe — Italy, Spain, France, and Portugal — underscoring that CCHFV is not a contained regional problem but an expanding global one.
Several constraints temper the study’s conclusions. Because human samples were drawn exclusively from febrile patients presenting to surveillance systems — rather than from the general population — the findings may overestimate community-level seroprevalence or reflect atypical exposure patterns. Tick collection and viral genome sequencing were not performed, leaving transmission dynamics and circulating strain phylogeny uncharacterized. Province-level analyses were also limited by small sample sizes in some areas, preventing granular geographic risk mapping.
Sources and further reading:
Lombe B, Munyeku-Bazitama Y, Kashitu-Mujinga G, et al. Seroprevalence of Crimean-Congo Hemorrhagic Fever Virus Infection in Humans and Domestic Ruminants, Democratic Republic of the Congo. Emerging Infectious Diseases. March 30, 2026.