The findings of this study are alarming, as they present the first report of the cocirculation of YFV, CHIKV, and DENV in the Greater Darfur region. The high seroprevalence of YFV antibodies was anticipated because of the previous vaccination campaign following the 2012 YFV epidemic [16]. However, the detection of a few YFV cases via RT‒PCR suggests that the virus is still actively circulating in the area. This persistence of YFV could be attributed to the significant cross-border movement between vaccinated and nonvaccine-susceptible areas due to conflict and political instability, which may have reduced vaccination coverage among residents [24, 15]. Alternatively, YFV might be maintained within populations of nonhuman primates [25].
DENV emerged in the area in 2015, starting in North Darfur, and soon after, an epidemic spread across Central, North, South, and West Darfur states, during which the co-transmission of WNV and CCHFV has also been documented [4, 10]. Additionally, a massive outbreak of CHIKV fever occurred in eastern Sudan between May 2018 and March 2019, with over 47,000 cases reported [7]. The region's heightened population dynamics, cross-border movement, trade, and influx of refugees contribute to its status as a hotspot for multiple vector-borne diseases, leading to annual outbreaks [26–29]. The low seroprevalence of CHIKV antibodies detected in this study suggests either that exposure to CHIKV might have occurred in East Sudan (with CHIKV-positive individuals being returnees) or that there is independent and unrecognized local transmission of CHIKV in the area [30, 31]. The latter hypothesis is more likely, given the detection of major arboviral disease vector in the region; Aedes albopictus [18].
The emergence and re-emergence of arboviral diseases pose a significant public health challenge, particularly in resource-limited settings with relatively weak health systems, where clinicians often rely heavily on clinical diagnosis [4, 10]. This reliance has resulted in numerous arboviral infections being misdiagnosed and treated as malaria [4, 10, 32]. The lack of publicly available up-to-date information on circulating diseases further limits the quality and capacity of healthcare services, as clinical diagnosis is heavily influenced by a clinician’s awareness of endemic diseases, as well as the health and travel history of patients [7, 33]. Also, coinfections with other parasitic infections, such as malaria, which are also characterized by fever, further complicates diagnosis. Without adequate laboratory diagnostic capacity to detect concurrent viral infections, especially when signs and symptoms become more severe and complicated, accurate diagnosis becomes even more challenging [21, 22, 34]. Additionally, the absence of a robust arboviral disease surveillance system significantly increases the risk of future epidemics [7].
To effectively combat arboviral diseases, it is crucial to establish a nationwide surveillance system that integrates both human and vector surveillance, with a strong focus on vector control. This system should include regular entomological surveys to monitor vector populations, assess their susceptibility to control measures, and detect the presence of arboviruses [35, 36]. Strengthening diagnostic capacity across national and regional laboratories is essential for accurate and rapid diagnosis, particularly in high-risk areas like refugee and IDP camps [37, 38]. Implementing standardized data collection and reporting systems will enable timely detection and response to outbreaks [39]. Building local capacity through ongoing training for healthcare workers, entomologists, and public health professionals is necessary, alongside community engagement to raise awareness about prevention and early detection [40]. Continuous monitoring and evaluation are key to ensuring the system's sustainability and effectiveness in controlling arboviral diseases.
In areas endemic for multiple infectious diseases, the use of molecular and serological diagnostic tests is particularly imperative, as symptoms can be similar and microscopic tests cannot detect viral infections [41]. Therefore, the country would benefit greatly from rebuilding its health system, with a focus on primary healthcare, by improving diagnostic capacity, surveillance, and reporting systems [12, 33, 39]. Moreover, adopting a One Health approach would be instrumental in the early detection of and response to outbreaks of arboviral diseases [36, 40]. The need for this approach is underscored by the increasing frequency of epidemics and epizootics of zoonotic arboviral diseases such as RVF, especially given the recent spatiotemporal changes in disease transmission [8, 9].
Arboviral epidemics are rapidly growing and expanding their geographical reach globally. In the absence of effective and sensitive surveillance systems for the early detection of arboviral disease outbreaks, these outbreaks will escalate into global threats. We, therefore, emphasize the urgent need for a nationwide surveillance system for arboviral diseases in Sudan. While the current local capacity is limited due to resource constraints, international support for building local health capacity and preparedness for the early detection and containment of arboviral epidemics is worth the global investment to avoid the emergence of larger multi-country pandemics. We also urge local and international health partners to support efforts in increasing local diagnostic capacity, surveillance, reporting, prevention and control of arboviruses. Special attention should also be given to the health of displaced persons living in overcrowded refugee and IDP camps.