Dengue is a major arboviral disease transmitted by mosquitoes of the Aedes genus, specifically Aedes aegypti and Aedes albopictus. It is a public health problem. According to the World Health Organization, nearly half of the world's population lives in at-risk areas, with a continuous increase in incidence over the past decades [1].

This expansion is linked to rapid urbanization, the globalization of trade, the intensification of human movement, and climate change, which are altering the geographical distribution of vectors [2, 3].

In Africa, dengue has long been underdiagnosed and underreported due to the high endemicity of malaria and the clinical overlap between these two acute febrile illnesses. However, recent data indicate a resurgence of epidemic outbreaks in several West African countries. They confirm active and sustained circulation of the virus in the region [4].

In Senegal, recurrent epidemics reported since 2017 indicate the gradual establishment of dengue in the national epidemiological landscape [5].

Tourist areas represent a particularly favorable context for the transmission of dengue. High human density, seasonal migratory flows, as well as environmental conditions conducive to the proliferation of larval habitats increase the risk of transmission. In Saly, these factors put both residents and visitors at risk.

In this context, the management of dengue in healthcare facilities, particularly private ones, presents diagnostic and therapeutic challenges. Despite the contribution of rapid diagnostic tests, the variability in clinical presentations can lead to practices that do not comply with international recommendations, particularly the inappropriate use of antibiotics and corticosteroids [1].

This study aims to describe the epidemiological, clinical, and serological profile of dengue cases diagnosed at the Urgences 24 clinic in Saly, in order to contribute to the improvement of management practices in a tourist area.

Patients And Methods

Study design

A retrospective descriptive case series was conducted at the Urgences 24 clinic in Saly, in the Mbour department of Senegal. The study was carried out over a six-month period, from May 17 to October 17, 2025. This clinic serves a diverse population, consisting of both local residents and seasonal visitors.

Population and sampling

The sampling was exhaustive and consecutive. The study population consisted of all patients suspected of having dengue who visited the clinic during the study period.  A suspected case was defined as any patient presenting with an acute fever (>38 °C) accompanied by at least one clinical sign compatible with dengue (headache, myalgia, arthralgia, or chills).  Patients were informed about the objectives of the study. Informed consent was obtained in accordance with national and international ethical guidelines. Confirmed cases were those whose diagnosis was validated by rapid diagnostic tests (RDTs) including the NS1 antigen and IgM and IgG antibodies.

Data collection

The information was collected using a standardized form with:

1. Sociodémographic data : age, sex, place of residence ;
2. Medical and vaccination history: chronic illnesses, smoking, alcohol consumption, COVID-19 vaccination ;
3. Environmental and behavioral factors: presence of stagnant water, use of insecticide-treated bed nets (MILDA) ;
4. Clinical signs and symptoms: fever, headaches, muscle aches, joint pain, cough, runny nose, chills, etc. ;
5. Biological tests: Dengue rapid diagnostic test (NS1, IgM, IgG), blood count, CRP (C-reactive protein), liver enzyme levels, kidney function (creatinine), prothrombin rate (PT) ;

Additional investigations: malaria rapid diagnostic test, thick smear, COVID-19 tests.

Statistical analysis

The data were entered into Excel and analyzed using RStudio version 4.4.0. Quantitative variables were described by mean ± standard deviation or median (range), and qualitative variables by counts and percentages. Univariate and bivariate analyses (Chi-squared and Fisher's tests) were performed. The significance level was set at p < 0.05. 95% confidence intervals were calculated.

Ethical considérations

The study was approved by the local ethics committee, and all data were handled anonymously and confidentially, in accordance with good ethical practices in biomedical research.

Results

General characteristics of study population

The population was mostly young and male. The average age was 29.4 years with a standard deviation of 11.7, and the sex ratio was 1.38. Subjects aged 15 to 30 were the most affected group (n=16; 37.2%). More than half of the patients lived in urban areas (Table I).

Table I: Characteristics sociodemographics of patients (N = 43)

A marked increase in the number of cases was observed starting in September, with an epidemic peak in September (Table II).

Table II: Monthly distribution of suspected and confirmed dengue cases

Consultation period and clinical presentation

The average time between the appearance of the first sign and seeking medical consultation was about 2 days. Fever was the main symptom, followed by headaches and muscle and joint pain.

Medical history

Of the 43 confirmed cases, seven were smokers, one was an alcoholic, two had high blood pressure, two had type 2 diabetes, and one was asthmatic. 31 of the patients had no medical history or particular condition. Seventeen (17) had been vaccinated against COVID-19, representing 39.5%.

Environmental and behavioral factors

The environmental characteristics of the patients, detailed in table III, highlight a lack of personal protection (MILDA) in the context of a high presence of stagnant water around homes. Among the 43 patients included, 11 (25.6%) used MILDA. The presence of stagnant water around homes was reported in 15 patients (34.9%).

Table III: Environnemental Factors

The clinical manifestations were dominated by fever and headaches, each observed in 69.8% of patients.

Table IV shows the distribution according to symptoms.

Comparison of suspected and confirmed cases

The clinical profile of the patients was compared according to serological status. Table 5 presents the comparison of demographic and clinical characteristics between suspected cases (negative) and confirmed cases (positive). Headaches, myalgia, and arthralgia were significantly more common in confirmed cases. Table V compares suspected and confirmed cases.

Table V: Comparison of characteristics between suspected and confirmed cases

The epidemic curve shows a gradual increase in cases from June, with a clear peak in September, followed by a decline in October.

Figure 1 : Epidemiological curve of dengue cases, May–October 2025

Biological confirmation was primarily based on the presence of IgM antibodies. Among the 43 patients included, several dengue serological profiles were identified. The most common profile was isolated IgG positivity (41.9%), followed by simultaneous positivity for NS1 antigen, IgM, and IgG (32.6%). Isolated detection of the NS1 antigen, indicating a very recent infection, accounted for 14.0% of cases. Profiles compatible with a recent infection in the seroconversion phase (isolated IgM positive) represented 9.3% of cases (Table VI).

Table VI : Distribution of dengue serological profiles according to NS1, IgM, and IgG markers

Serological profile of patients

More than a third of the patients had laboratory-confirmed dengue (table VII).

Table VII: Positivity of dengue serological markers and case classification

Other Data

Hematologically, lymphopenia and an elevated CRP were the most frequent abnormalities in confirmed cases. Patients (suspected and confirmed cases) underwent rapid diagnostic tests (RDT) for malaria/thick smear and COVID-19 tests. All of these investigations were negative in confirmed dengue cases, thus ruling out any biological co-infection in this group. The malaria RDT was performed on twenty (20) patients, the thick smear on nineteen (19). In three (3) patients who had a negative malaria RDT, a thick smear was carried out to formally rule out associated malaria. The COVID test was performed on 13 patients. Concurrent screening for both malaria and COVID-19 was performed on 3 patients. Prothrombin time (PT) was measured in 7 of our patients and ranged from 46 to 75%, with an average of 61.6% ± 10.4. Serum creatinine, also measured in seven (7) patients, ranged from 6.1 to 15.3 mg/dL, with an average of 10.4 ± 3.1 mg/dL.

Table VIII shows the distribution of patients according to the results of their paraclinical examinations.

Table VIII: Distribution by results of biologic exam

Bivariate and multivariate analysis

The bivariate analysis identified several clinical signs strongly associated with the biological confirmation of dengue. Logistic regression then helped adjust these results.

The analysis shows that the clinical triad of headaches, muscle pain, and joint pain is the strongest predictor of dengue in this tourist area. In a bivariate analysis, patients with headaches were 3.4 times more likely to have confirmed dengue compared to other febrile suspects (p=0.005). Although multivariate adjustment shows a reduction in statistical significance (due to the strong collinearity between these clinical symptoms), the overall effect remains clinically substantial. Age also seems to be a marginal risk factor, with a 5% increase in risk per year of age (p=0.095 in multivariate analysis).

Table IX: Biavariate et multivariate analysis