Investigation of Dengue Fever Outbreak in Riyadh City, 2023

Dengue Fever (DF) is a mosquito-borne viral infection caused by the dengue virus, primarily transmitted by Aedes mosquitoes, particularly Aedes aegypti. DF poses a substantial global health threat, with approximately 100-400 million cases occurring annually, resulting in significant morbidity and mortality. It manifests with fever, headache, joint and muscle pain, rash, and, in severe cases, hemorrhagic fever or shock. The global burden of DF is highest in tropical and subtropical regions, particularly in Southeast Asia, the Americas, and the Western Pacific, where the environmental conditions favor mosquito breeding.

In Saudi Arabia, DF has emerged as a public health challenge, particularly in urban centers like Jeddah, Jazan, Riyadh. Rapid urbanization, increased travel, and favorable climatic conditions have contributed to the rise in dengue cases. Despite ongoing vector control efforts, dengue outbreaks continue to occur, necessitating detailed epidemiological investigations to inform effective public health responses. Our investigation into the Riyadh outbreak from October to December 2023 aimed to understand the epidemiology, clinical manifestations, and control measures associated with DF during this period.

            We conducted an outbreak investigation ( case-control study ) using data from the Health Electronic Surveillance Network (HESN) and phone interviews. We defined a dengue case as an individual with fever and at least one of the following symptoms: headache, joint and muscle pain, retro-orbital pain, nausea, vomiting, swollen glands, rash, confirmed by a positive RT-PCR, Ns1, or IgM test. Controls were Riyadh residents without clinical DF symptom.

            Our study shows that during the dengue fever outbreak in Riyadh from October to December 2023, a total of 77 cases were identified. The mean age of affected individuals was 38.6 years, with the 30-39 age group representing the largest proportion at 33.7%. Males accounted for 66% of the cases. The calculated attack rate was 0.0009%, indicating a relatively low incidence but reflecting a potentially underreported burden given the rapid spread and diverse clinical presentations. This demographic distribution aligns with global patterns where middle-aged individuals are often more exposed due to occupational or lifestyle factors.

Epidemiologically, our analysis identified significant associations between the presence of stagnant water and dengue cases. Specifically, 77.9% of the cases had stagnant water in or around their homes, resulting in an odds ratio (OR) of 2.79, underscoring the critical role of environmental factors in facilitating mosquito breeding and disease transmission. In addition, the use of mosquito repellent was prevalent among 51.9% of the cases, yielding an OR of 4.47, suggesting a behavioral response to perceived risk. However, only 6.5% reported wearing full protective clothing, which was associated with a substantially lower risk of infection OR=0.09, highlighting a gap in comprehensive personal protective measures.

Editorial note: We found that the dengue fever outbreak in Riyadh from October to December 2023 was significantly influenced by urban expansion and environmental conditions that favored mosquito breeding. Our analysis showed that males and individuals aged 30-39 years were the most affected demographics. Key risk factors included the presence of stagnant water around homes, inadequate use of mosquito repellents, and insufficient protective clothing. These findings highlight the critical role of environmental management and personal protection in controlling the spread of dengue fever.

Moving forward, we recommend strengthening public health interventions focused on effective vector control and community education. Enhanced surveillance systems are crucial for early detection and response to outbreaks. Public awareness campaigns should emphasize the importance of eliminating mosquito breeding sites and using personal protective measures. Coordinated efforts between health authorities, local governments, and communities will be essential to mitigate the impact of dengue fever and prevent future outbreaks in Riyadh.

Table 1 Demographic Characteristics of Dengue Fever Cases and Controls