This descriptive analytical study assessed the seroprevalence and progression of dengue virus infection among patients at CERBA over a 9-month period, from 1 January to 30 September 2023.

A total of 4,484 patients seen at or referred to the CERBA laboratory for dengue serological testing during the study period were consecutively enrolled, regardless of age, sex, origin or ethnic group.

Patients were eligible if they presented with febrile illness and clinical suspicion of dengue as indicated by the referring physician. Individuals with incomplete clinical or demographic information, or those whose serum samples were insufficient or inadequate for testing, were excluded from the study.

Venous blood samples were collected in either dry tubes or EDTA tubes. Following centrifugation at 4,000 rpm for 5 minutes, serum or plasma was extracted and used for dengue testing. Serological tests were conducted immediately after sample collection to ensure prompt availability of results.

Dengue virus infection was diagnosed using the SD Bioline Dengue Duo Rapid Detection Kit (Standard Diagnostics Inc., Korea), following the manufacturer’s instructions. This rapid test detects the NS1 antigen and anti-dengue virus IgG/IgM antibodies in serum, plasma, or whole blood. According to the manufacturer, the assay has a sensitivity of 92.4% for NS1 antigen and 94.2% for IgG/IgM antibodies, with specificities of 98.4% for NS1 antigen and 96.4% for IgG/IgM antibodies. These performance characteristics indicate high diagnostic accuracy and support the reliability of the results obtained in this study.

Data were processed using Microsoft Excel version 2019 and Statistical Package for Social Sciences (SPSS) version 26.0 (SPSS Inc., Chicago, IL, USA). Multivariate logistic regression was used to assess the effects of age and gender on dengue infection. Statistical differences were deemed significant at p < 0.05.

The study population comprised 60.1% females (2693/4484) and 39.9% males (1791/4484). The mean age was 26.80 ± 16.24 years (range: 0 - 93 years) overall, with 27.75 ± 15.86 years (range: 0 - 90 years) in females and 25.38 ± 16.70 years (range: 0 - 93 years) in males. The age group 16 - 30 years was the most represented, accounting for 41.6% (1864/4484) of the study population ( Table 1 ).

NS1: Non-structural Protein 1, Immunoglobulin M (IgM), Immunoglobulin G (IgG).

It is noteworthy that 52.5% (2352/4484) of the study population tested positive for NS1 Ag, 32.1% (1440/4484) for IgM, and 36.8% (1649/4484) for IgG. The age group 16 - 30 years had the highest positivity rates for NS1 Ag (57.3%, 1069/1864) and IgM (30.6%, 571/1864), while the age groups 46 - 65 years and > 65 years showed the highest IgG positivity rates ( Table 1 ).

The overall dengue seroprevalence was 57.5% (2578/4484), with the following specific rates: 37.9% (1701/4484) NS1 Ag⁺, 18.2% (817/4484) IgM⁺, 6.9% (309/4484) NS1 Ag⁺/IgM⁺, 6.3% (282/4484) NS1 Ag⁺/IgG⁺, and 1.3% (60/4484) triple positive ( Table 2 ). Individuals with past infections (positive for IgG only) constituted 23.5% (1053/4484) of the study population.

Multinomial regression analysis revealed that the age group 16 - 30 years was significantly more likely to test positive for NS1 Ag compared to children under five years old (OR = 1.487 [1.158 - 1.911], p = 0.002). Conversely, individuals above 65 years were significantly less likely to test positive for NS1 Ag compared to the same reference group (OR = 0.517 [0.325 - 0.824], p = 0.005). No significant differences in IgM positivity were observed across sex and age groups ( Table 3 ).

NS1: Non-structural Protein 1, Immunoglobulin M (IgM), Immunoglobulin G (IgG).

NS1: Non-structural Protein 1, Immunoglobulin M (IgM), Immunoglobulin G (IgG).

Suspected febrile cases tested for dengue throughout the year showed fewer cases from January to August, with a gradual increase in the proportion of positive cases over the months. NS1 Ag-positive cases accounted for 4.8% (6/126) and 6.9% (5/72) in January and February, respectively. The proportion of positive cases remained below 50% in May (37.0%, 20/54), June (47.8%, 33/69), and July (40.7%, 44/108). However, the percentage of positive cases increased to 70.3% (64/91) in March, 81.4% (57/70) in April, and 56.1% (83/148) in August. Notably, most suspected cases, 83.5% (3746/4484), were recorded in September, with 54.5% (2040/3746) testing positive for NS1 Ag ( Figure 1 ).

The study revealed that females accounted for a larger proportion of the study population (60.1%), yet males exhibited slightly higher rates of NS1 antigen positivity (55.1% vs. 50.7%). This pattern has been observed in other studies, where males are often reported to have higher susceptibility or exposure risk due to behavioral and environmental factors, such as outdoor activities that increase contact with Aedes mosquitoes [4] [11] [12] [18] . However, the gender-related differences in dengue prevalence remain inconsistent across studies and may vary depending on local dynamics [10] [19] .

The age group 16 - 30 years showed the highest positivity for NS1 antigen (57.3%), indicating active infection, which aligns with literature suggesting that young adults are at a higher risk due to mobility and exposure in urban or peri-urban settings [9] [18] . Similarly, the observed high IgG positivity in older age groups (>46 years) reflects cumulative exposure to dengue virus over time, consistent with studies showing that older populations are more likely to have antibodies due to prior infections [20] - [22] .

The overall seroprevalence of 57.5% reflects a high burden of dengue in the study population, which is comparable to findings from endemic regions in Asia and Latin America [23] [24] . The dominance of NS1 antigen positivity (52.5%) suggests ongoing transmission, while the significant proportion of IgM-positive cases (32.1%) indicates recent infections. The high rate of IgG positivity (36.8%) reflects both prior exposure and the endemic nature of dengue in the region [4] [6] [25] .

Notably, the study identified a substantial number of cases with multiple serological markers, including triple-positive cases (1.3%), which were found to be predictive of severe thrombocytopenia linked to dengue infection and a higher risk of mortality. Such profiles are indicative of either sequential infections with different dengue serotypes or co-circulation of serotypes, which aligns with findings in regions where multiple serotypes are endemic [6] [11] [12] . However, our study did not include laboratory confirmation of circulating serotypes. Incorporating serotype data in future investigations would allow for analysis of their distribution, potential shifts, and possible associations with disease severity and transmission dynamics, thereby improving outbreak preparedness.

Positioning The seasonal dynamics observed in this study, with a significant spike in dengue cases during September (83.5% of cases, with 54.5% NS1 antigen positivity), align with the well-documented correlation between dengue incidence and climatic factors [5] [6] . Increased transmission during rainy seasons is attributed to optimal breeding conditions for Aedes aegypti, the primary vector [25] . The gradual rise in positive cases from January to August, followed by a peak in September, is consistent with the previous studies conducted by our research team, showing that peak of DENV infection in Burkina Faso generally occurred between October and November [4] [11] [12] .

The burden of dengue in Burkina Faso, as indicated by this study, is consistent with the increasing incidence of dengue reported globally [17] . African countries, including Burkina Faso, are increasingly contributing to this burden, reflecting expanding geographic transmission due to urbanization, climate change, and inadequate vector control measures [16] . The findings highlight the critical need for enhanced surveillance systems to monitor serotype dynamics and guide targeted interventions. The high seroprevalence underscores the importance of implementing integrated vector management strategies and strengthening diagnostic capacities, particularly for serological markers like NS1, IgM, and IgG, which are pivotal in resource-limited settings.

This study contributes to the growing body of evidence on the epidemiology of dengue in Africa and underscores the importance of continuous monitoring and intervention strategies. The high prevalence of dengue calls for urgent action to mitigate the impact of future outbreaks through improved surveillance, public health education, and vector control efforts.

Although multinomial regression highlighted demographic patterns (e.g., male sex, young adult age group), potential confounders such as socioeconomic status, access to healthcare, and travel history were not included in the analysis. Their absence may limit interpretation of independent associations. Future studies should incorporate these covariates to better disentangle the effects of demographic and behavioral risk factors.

Other limitations include selection bias, as only patients presenting for testing were included, and possible misclassification due to serological cross-reactivity with other flaviviruses. The cross-sectional design also limits causal inferences and the ability to track temporal changes at the individual level.

The high seroprevalence observed underscores the urgent need for strengthened surveillance systems that integrate serotype monitoring, climatic variables, and vector indices. Public health interventions should prioritize targeted vector control campaigns during peak rainy months, school- and workplace-based awareness programs focusing on young adults and males, and improved diagnostic capacity at primary health facilities. Furthermore, incorporating serotype-specific data into predictive models would allow health authorities to anticipate severe outbreaks linked to shifts in circulating strains. Finally, longitudinal cohort studies with robust sociodemographic and clinical data are essential to clarify the dynamics of infection, immunity, and severity over time.