July 2024: A study was launched to investigate the presence and prevalence of arboviruses across nine African partner countries in the EXPANDIA project.
The study sought to address the significant public health challenges posed by vector-borne diseases, particularly in sub-Saharan Africa, while filling the data gap regarding the presence of arboviruses in the region. Partner reference laboratories frequently reported arboviral infections, but these claims could not always be confirmed due to the lack of appropriate and accessible testing methods.
Vector-borne diseases, primarily transmitted through the bites of infected mosquitoes, are a major public health concern globally with African countries facing an escalating burden. Among the most prevalent arboviral diseases worldwide are Dengue fever, Chikungunya virus and Zika virus. Recent decades have seen a marked increase in the incidence and geographical spread of these viruses, driven by contributory factors such as global travel, urbanization, climate change, and gaps in vector control strategies. Consequently, many non-endemic regions, including sub-Saharan Africa, are increasingly experiencing outbreaks of these viruses.
Dengue, Chikungunya and Zika share similar epidemiology and transmission pathways. While the clinical symptoms of these infections are often mild or non-specific, they can lead to serious complications. For instance, Zika infection has been linked to neurological and autoimmune complications, as well as foetal microcephaly in cases of maternal infection. Although Dengue and Chikungunya infections are associated with low mortality, their endemic presence can lead to severe conditions such as Dengue haemorrhagic fever syndrome, which has a high mortality rate of 10-15%. High mosquito vector density can also result in large Chikungunya outbreaks and epidemics.
Despite their significant impact on human health, the prevalence and distribution of these arboviruses in many African countries remain poorly understood due to limited surveillance and diagnostic capacities. This knowledge gap hinders effective public health responses, including outbreak prediction, prevention and control measures. The co-circulation of these viruses, alongside other endemic diseases such as malaria and yellow fever, further complicates clinical diagnosis and management, calling for reliable diagnostic tools and strategies.
Prof. Marycelin Baba, based in Nigeria and a key researcher of the EXPANDIA project network, emphasizes the underestimation of the burden of arboviral infections in Africa. She states: “One of the main issues is the endemic presence of malaria and typhoid fever in the region. Malaria is generally ascribed to all febrile illnesses presented at Point of Care unless confirmed through laboratory testing. Febrile patients often exhibit symptoms that are believed to indicate malaria or typhoid, but these symptoms are also common to arbovirus infections. As a result, patients often seek medical care only if their fever persists after self-medication with anti-malarial and antibiotics treatments, making it difficult to isolate or detect the virus after that.” This practice is often associated with the gradual development of antimicrobial resistance in wrongly treated pathogens, such as malaria.
The EXPANDIA project aimed to understand the circulation dynamics and disease burden of these viruses on the African continent. Additionally, the project sought to evaluate the diagnostic accuracy of tests, based on the needs and operational conditions of laboratories in both urban and peripheral settings, to improve clinical diagnosis and patient care, particularly in regions where vector-borne diseases coexist.
The study involved teams of partner scientists from nine reference laboratories in ICGEB Member States Angola, Burkina Faso, Cameroon, Ethiopia, Ivory Coast, Kenya, Nigeria, Senegal and Zimbabwe, with the Zimbabwean scientists performing arbovirus sample screening for the first time in their history. Dr. Mariana Ulinici, clinical studies coordinator in the ICGEB Molecular Virology laboratory, explains that the study employed a multi-phase, cross-sectional design to evaluate the prevalence and diagnostic accuracy of identified tests. African scientists collected serum samples from patients with acute febrile illness presenting within five days post-onset. These specimens were screened using an RT-qPCR capable of detecting viral RNA of Zika, Dengue, and Chikungunya in the same reaction. Positive samples, along with a selection of negative samples, advanced to the next step to evaluate and compare the diagnostic accuracy of rapid tests against the reference standard triplex RT-qPCR. “This step allowed for a balanced assessment and more robust evaluation of the diagnostic accuracy of the compared kits,” notes Dr. Ulinici. “We are now assessing the sensitivity, specificity and overall performance of the tests in detecting arboviral infections.”
The tests considered are rapid antigen tests for Dengue, selected for their portability, ease of use and preliminary performance results. Dr. Alessandro Marcello, scientific coordinator of EXPANDIA, highlights the importance of antigen tests in many community and peripheral laboratories in Africa lacking resources and skilled personnel. “In case of an outbreak, antigenic tests are very useful for the initial screening of samples that are then sent to national reference laboratories for confirmation by molecular tests. This would avoid considerable costs for transporting samples from remote areas and long waiting times for patients. Having a clinical diagnosis in the shortest possible time is fundamental to guide patients’ behaviour and prevent further spread of the infection. The consequence of not having this service means that an infected person could take a mis-prescribed medicine before the nature of the infection is established with certainty”.
To address this issue, the project tested rapid kits that can detect the NS1 protein of Dengue virus which signals an ongoing infection. Prof. Baba remarks that in some settings, NS1 rapid detection tests can be as efficient as PCR, allowing for the confirmation of positive cases and ongoing infections on the spot.
So far, albeit on a small sample, the study confirmed the presence of the tested pathogens in sub-Saharan Africa, with all three dengue, chikungunya, and zika viruses detected in at least one partner country. This demonstrates the need for a surveillance plan by public health systems at national and regional levels. Effective diagnostic tests can enhance surveillance activities, case management and inform public health responses. As such, the project team explores how these tools can facilitate early detection and timely management of cases to prevent outbreak escalation. Given the complexity and urgency of the situation, this study is poised to make a significant contribution to public health in Africa, providing evidence-based insights that can guide resource allocation, control measures and improve clinical outcomes for affected individuals.
