Epidemiology of Dengue Fever in Somaliland: Clinical Features, and Serological Patterns from a Retrospective Study

This study provides initial insights into the epidemiology of dengue in Somaliland, though further research is needed to establish robust baseline data, highlighting its prevalence and distinct characteristics. This study involved 1,410 subjects with diverse sociodemographic backgrounds. The results revealed a 12.41% prevalence of dengue among positive cases, indicating its significant presence as a public health concern in Somaliland.

The number of males infected was 60.57%, which is higher than the female infection rate in our study, in contrast to the findings of previous studies, which reported a predominance of female subjects [10,11,12,13]. This gender disparity may be attributed to factors such as differences in exposure to mosquito vectors due to occupational or behavioral patterns or variations in healthcare-seeking behavior between males and females in the study population. In addition, we found that most infected dengue patients (45.1%) were 19–38 years of age, followed by those aged ≥ 39 years (40.6%). This finding is comparable to those of a study conducted in Thailand (40.69%) [14] and Singapore (50.8%) [15]. The high vulnerability of this age group to dengue in adult populations may result in elevated infection risks due to increased exposure to mosquito vectors during outdoor activities. Additionally, the clinical presentation and manifestations of the disease in adults are often more subtle and challenging to diagnose than those in pediatric cases [16, 17].

This study examined the prevalence of this disease across four distinct areas of Somaliland (Somalia). The findings revealed that most confirmed dengue cases were concentrated in the Togdher and Awdal regions, with the Marodijeex and Sahel regions also reporting infections (Table 1). The geographical distribution of the cases provides valuable insights into the spread of the disease within the country. The northwestern part of Somaliland, encompassing Awdal and Waqooyi Galbeed (Maroodi Jeex), has experienced a decline in precipitation and an increase in average temperature over the last 30 years.

These climatic shifts towards hotter and more arid conditions may influence the prevalence of mosquito-transmitted illnesses such as dengue fever, given that mosquito populations are responsive to environmental changes [18, 19]. The elevated incidence of dengue in Togdheer (Burao), Awdal (Borama), and Maroodijeex (Hargeisa) in Somaliland can be attributed to a multifaceted interaction involving mosquito ecology, human movement trends, and the capabilities of the local healthcare infrastructure.

The study found that of 175 confirmed dengue cases, 103 (58.9%) of dengue cases were from urban environments, compared to 72 (41.1%) from rural areas. This demonstrates the clear urban predominance of dengue cases in Somaliland. This supports findings from other regions [20,21,22]. However, contradictions have also emerged [23, 24]. Several factors may contribute to higher urban prevalence, including greater population density in cities, poor urban sanitation infrastructure, abundance of artificial water containers that serve as vector breeding sites, and increased human movement and interaction in urban areas. The contradictions in some studies could be due to regional variations in urbanization patterns, climate, vector ecology, or socioeconomic factors that influence dengue transmission dynamics.

Urban areas in Somaliland are struggling with water storage and waste management, thereby fostering the breeding of Aedes mosquitoes. Warmer city microclimates may lengthen the mosquito breeding season. Although specific studies of Somaliland are limited, research in other areas offers insights. For example, a study in Delhi found that lack of tap water access significantly increased dengue virus seropositivity [25]. In Brazil, inadequate sanitation is associated with a high incidence of dengue [26]. A Colombian study showed that monthly insecticide treatments in street catch basins significantly reduced the number of Aedes larvae and dengue cases (Ocampo et al., 2014). Effective environmental management, including proper sanitation, waste management, and water systems, has controlled disease vectors such as dengue [27]. In Guangzhou, China, artificial lakes have been linked to increased dengue outbreaks by providing additional mosquito breeding sites [27].

Patients with dengue often exhibit a range of clinical symptoms [28]. In our study, the most prevalent manifestations were elevated body temperature (86.70%) and gastrointestinal disturbances, such as emesis and nausea (86.70%) (Table 2). These findings align with those of previous studies of dengue symptomatology [29,30,31]. Other commonly observed symptoms in dengue cases include gastrointestinal issues (n = 150, 86.70%), myalgia (n = 122, 70.52%), and respiratory symptoms, such as cough and headache. This was Followed by chest pain (79.19%) and rashes (52.02%) [31,32,33].

The high prevalence of neurological symptoms (36.9%) observed in our study is a significant finding. In some cases, the neurological symptoms observed primarily included confusion, altered consciousness, and seizures. Our finding was higher than that of Carod-Artal et al. (2013), who found neurological complications in 21% of patients with dengue [34]. However, other studies have reported conflicting results. For instance, Kulkarni et al. (2021) reports a lower percentage, stating that “Of these, 154 (2.64%) had neurological manifestations,” [35] and a study conducted in India reports neurological complications due to dengue fever at 9.5%, with the most prevalent symptoms, each occurring in 73.3% (n = 22) of cases, being cephalalgia, impaired consciousness, and convulsions [35, 36]. This discrepancy could be attributed to differences in study populations, clinical settings, direct viral effects or diagnostic criteria used, and delayed healthcare-seeking behavior due to limited access to healthcare facilities, which can lead to the progression and exacerbation of neurological conditions.

In our investigation, the majority of dengue-positive cases were classified as mild and were managed on an outpatient basis. Fifteen patients (8.57%) required hospitalization. According to the World Health Organization classification [37], the primary cause of hospitalization was severe dengue, accounting for eight cases (53.3% of hospitalized patients), and dengue with warning signs, comprising seven cases (46.6% of hospitalized patients). Among these, two cases involved young individuals, whereas five cases were within the 19–38 age range. However, nearly half of the severe cases occur in adults aged ≥ 39 years, similar to those reported in Saudi Arabia [1] and India [2].

Our study found that a higher proportion of hospitalized patients were older (≥ 39 years). Although this observation suggests a potential correlation between increasing age and disease severity, it is important to note that our study did not explicitly examine the role of comorbidities in this relationship. Comorbidities such as diabetes, hypertension, and cardiovascular disease are more prevalent in older populations and are known to complicate dengue management and lead to poorer outcomes. Several studies have highlighted the association between comorbidities and increased severity of dengue infection such as diabetes, and patients with pre-existing diabetes were associated with dengue severity [38, 39]. The higher hospitalization rate among older patients in our study could be attributed age-related physiological changes affecting the immune response to dengue infection, a higher likelihood of comorbidities exacerbating the disease course, and potentially delayed healthcare-seeking behavior leading to more advanced disease at presentation. Dengue infection in children often results in severe vascular permeability and a sudden onset of shock [40, 41].

Our study revealed an unexpected finding regarding the severity of dengue cases among children in Somaliland. Contrary to established literature, which typically identifies children as a high-risk group for severe dengue [42, 43], we observed relatively few pediatric cases with severe symptoms. This discrepancy warrants careful consideration and may have important implications for understanding the dengue epidemiology in this region.

Several factors could explain this observation. First, our reliance on data from public hospital laboratories may have introduced a sampling bias, potentially underrepresenting pediatric cases treated in other healthcare settings or those not seeking formal medical care. Second, differences in care-seeking behavior among parents in Somaliland could result in fewer children with milder symptoms being brought to hospitals, thus skewing our sample towards more severe adult cases. Finally, it is possible that this finding reflects a genuine epidemiological trend unique to Somaliland, where adults may be more severely affected by factors such as circulating serotypes or population immunity profiles.

The study found an overall prevalence of 175 (12.41%), which was comparable to findings in Puntland state, Somalia (12.3%) [44], but lower than those reported in Sudan (42%) and Kenya (61.2%) [45, 46]. These variations could be attributed to differences in environmental factors, the size of the samples analyzed, and the methods used for diagnosis. The findings revealed that 8.57% of dengue cases tested positive for dengue IgM antibodies, which aligns with the 8% prevalence reported in Indian studies [47]. However, 28.32% reported from Mangaluru [48] and 14.7% in Italy [49], and this study revealed a significant occurrence (84.57%) of dengue NS1 antigen among the tested subjects which is almost close with study done from Puntland [44]. Detection of the NS1 antigen is particularly useful during the early stages of dengue infection, especially from the third to fifth day after symptom onset, when virus levels in the bloodstream may be too low for detection and the immune system has not yet produced sufficient anti-IgM antibodies for reliable identification [50]. These discrepancies are likely attributable to various factors including the timing of sample collection, differences in testing methodologies, diverse patient demographics, and specific dengue serotypes involved. The small percentage of cases (6.85%) showing both NSI and IgM positivity is likely due to the short time frame during which both markers can be simultaneously detected [51, 52].

This study identified significant correlations between clinical manifestations and hospitalization in patients with dengue, specifically focusing on rash and myalgia, corroborating previous research on the relevance of these symptoms in disease progression and severity [53,54,55]. The strong association between rash and hospitalization aligns with the findings of Tiga-Loza et al. (2020), who observed that rash persisting for a month after fever onset was prevalent among hospitalized patients [56]. This correlation was further substantiated by Santos et al. (2004) and Jelinek (1997), who recognized rashes as an indicator of severe dengue. The underlying pathophysiological mechanisms likely involve increased vascular permeability and immune-mediated processes.

The significant correlation between myalgia and hospitalization aligns with the findings of Suppiah et al. (2018) and Mallhi et al. (2015), who reported a higher prevalence of myalgia in hospitalized patients with dengue [57,58,59]. Interestingly, fever, a primary dengue symptom, showed no significant association with hospitalization, which is consistent with the results of other studies [60, 61]. This may be due to the timing of fever onset and emergence of severe symptoms.

Despite the moderate effect size for cough, which lacked statistical significance, further investigation is required. Respiratory symptoms are generally not linked to dengue; however, Rodrigues et al. (2014) suggested that pleural effusion may be more common in severe dengue cases than previously thought [62]. Increased pulmonary involvement could be due to the virus affecting multiple organ systems, the host inflammatory response, or complications from severe vascular leakage [63].

The lack of significant associations for symptoms, such as headache, chest pain, and gastrointestinal disturbances, is notable. These results contrast with those of Paraná et al. (2024), who found strong correlations between headache, chest pain, abdominal pain, and dengue severity [42]. This difference may stem from variations in sample size, study design, regional differences in dengue presentation, timing of symptom assessment, predominant virus serotypes or strains, healthcare accessibility, treatment protocols, and prevalence of comorbidities or confounding factors among the study populations.

In 2024, the dengue incidence reached its highest point in June, subsequently declined from August, and slightly increased in September (Fig. 1), potentially influenced by shifts in climate and precipitation patterns. Somaliland experiences temperatures ranging from 27 °C to 37 °C, with major rainfall periods occurring in spring (April–June) and fall (October–December) [64]. The fluctuations in dengue incidence observed on a monthly basis may be attributed to alterations in the climatic conditions and precipitation patterns. Climate variability has been shown to have a significant impact on the occurrence of dengue fever across multiple studies [65, 66].

This study provides insights into dengue fever occurrence in Somaliland; however, it has several limitations. The reliance on rapid diagnostic tests, which have limited sensitivity and specificity compared to more advanced methods such as PCR, may have affected the accuracy of case detection. The absence of data on circulating dengue serotypes limits our understanding of disease dynamics.

The study’s retrospective nature and focus on a single public hospital may not capture all cases, especially milder cases that do not seek hospital care. The short study period may not reflect long-term trends.

Additionally, the study did not incorporate climatic data, such as precipitation or temperature, which could have provided insights into seasonal patterns. The use of secondary data sources introduces potential issues of incompleteness or omission. Some cases lacked comprehensive clinical details and there was an absence of virological or genomic data. Long-term patient outcomes were not available, limiting the assessment of prognosis and treatment efficacy.

This study could not determine the origin of dengue infections or provide detailed information on disease transmission patterns. Despite these limitations, this study offers valuable preliminary data on dengue fever in Somaliland and establishes a foundation for future studies. To address these constraints, future research should prioritize primary data collection, including comprehensive clinical documentation, advanced diagnostic techniques for viral characterization, and collection of local meteorological data alongside dengue case data. Implementing a robust surveillance system to track case outcomes and transmission patterns would significantly enhance our understanding of dengue fever dynamics in this region.

This study provides crucial initial insights into the epidemiology of dengue in Somaliland, revealing distinct characteristics that differ from those of other regions. These findings highlight the urban predominance of cases, the disproportionate impact on adult populations, and the prevalence of acute infections, underscoring the need for targeted interventions and enhanced surveillance. These results lay the foundation for future research and policy decisions, emphasizing the importance of strengthening vector control measures, diagnostic capacity, and public awareness. Despite these limitations, this study serves as a stepping stone for more comprehensive investigations to address knowledge gaps and develop effective strategies for combating dengue in Somaliland and similar settings. The insights gained from this research contribute to a broader understanding of dengue epidemiology in understudied regions and underscore the importance of context-specific approaches in global dengue control efforts.

The datasets utilized in this study are not publicly accessible because of privacy concerns. However, interested parties may contact the corresponding author to request access to the data, thereby supporting the findings presented herein. Any such request is evaluated on a case-by-case basis.

DENV: Dengue virusDHF: Dengue hemorrhagic fever

DSS: Dengue shock syndrome

ELISA: Enzyme-linked immunosorbent assay

IgM: Immunoglobulin M

NS1: Non-structural protein 1

RDTs: Rapid diagnostic tests

We extend our gratitude to all study participants for their kind cooperation. Additionally, we thank the University of Burao for providing the ethical approval letter necessary to conduct this research. We also thank public laboratories for their support.

Not applicable.

Authors and Affiliations

• • • School of Medical Laboratory Science and Department of Microbiology and Veterinary Public Health, University of Burao, Somaliland, Somalia

Dek Kahin Yosef

• • Jigjiga University, Burao, Ethiopia

Dek Kahin Yosef

• • Department of Microbiology and Veterinary Public Health, College of Veterinary Medicine, University of Burao, Burao, Somalia

Dek Kahin Yosef, Ahmed Saeed Ismail, Halima Ahmed Hassan & Mohamed Ahmed Hassan

• • School of Nursing and Midwifery, College of Medical and Health Science, Edna Aden University, Hargeisa, Somalia

Barwaqo Saleban Awil

Contributions

DKY conceptualized and designed the study, collected and analyzed the data, interpreted the results, drafted the manuscript, and critically reviewed and approved the final version. ASI, BSA, HAH, and MAH contributed to study design, data collection, analysis and interpretation of results, and manuscript review. All authors reviewed the manuscript, agreed to the target journal for submission, and accepted responsibility for all aspects of the study.

Corresponding author

Correspondence to
Dek Kahin Yosef.

Ethics approval and consent to participate

This study was approved by the Ethics Review Committee (ERC) of the University of Burao School of Postgraduate Studies and Research. The ERC waived the requirement for informed consent due to the retrospective nature of the study and the use of existing de-identified data under the approval number (Ref. No. UoB/SPGSR/18/2024). The study was conducted in accordance with relevant ethical guidelines and regulations.

Consent for publication

Not applicable.

Clinical trial number

Not applicable.

Competing interests

The authors declare no competing interests.

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