Dengue fever, characterized by its elusive nature, lacks a definitive treatment regimen. The therapeutic approach centers on alleviating the symptomatic pain. For the majority of dengue cases, which are manageable in a domestic setting, analgesics are administered. Acetaminophen (paracetamol) is frequently employed to mitigate discomfort. Non-steroidal anti-inflammatory drugs (NSAIDs), including ibuprofen and aspirin, are generally avoided due to their propensity to exacerbate bleeding risks.
In cases of severe dengue, clinical intervention necessitates hospitalization. The global prevalence of dengue has escalated markedly over recent decades. The World Health Organization (WHO) reported an alarming rise in cases from 505,430 in 2000 to approximately 5.2 million by 2019. Despite this surge, many instances of dengue remain asymptomatic or mildly symptomatic, leading to significant underreporting. Misdiagnosis as other febrile illnesses compounds this issue.
The year 2023 witnessed a staggering increase in dengue cases, with over 80 countries across all WHO regions affected. This unprecedented spike, surpassing 6.5 million cases and resulting in over 7,300 dengue-related fatalities, underscores the crisis. Contributing factors include the altered distribution of vectors, primarily Aedes aegypti and Aedes albopictus mosquitoes, and climatic anomalies such as the El Niño phenomenon, which have intensified in 2023. Other influences include weakened health systems due to the COVID-19 pandemic, political and economic instability, and extensive population movements.
Modeling estimates suggest a staggering 390 million dengue virus infections annually, with 96 million manifesting clinically. Another study suggests that approximately 3.9 billion individuals are at risk of dengue virus infection. The disease now persists endemically in over 100 countries across the WHO regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia, and the Western Pacific, with Asia bearing the brunt, representing around 70% of the global burden. Dengue is also infiltrating new territories in Europe, the Eastern Mediterranean, and South America.
In 2023, the highest incidence of dengue was reported, with the Americas region documenting 4.5 million cases and 2,300 deaths. Asia saw a significant number of cases, including Bangladesh (321,000), Malaysia (111,400), Thailand (150,000), and Vietnam (369,000).
Transmission Dynamics
Mosquito-Borne Transmission
The dengue virus is primarily disseminated to humans via the bites of infected female mosquitoes, predominantly Aedes aegypti. Although other Aedes species can act as secondary vectors, Aedes aegypti remains the principal transmitter. Notably, 2023 saw an uptick in dengue transmission by Aedes albopictus (tiger mosquito) in Europe.
Upon feeding on an infected host, the virus undergoes replication within the mosquito’s midgut before spreading to secondary tissues, including the salivary glands. The period between viral ingestion and subsequent transmission to a new host, known as the extrinsic incubation period (EIP), typically spans 8–12 days when temperatures range from 25–28°C. Variations in EIP can occur due to factors such as daily temperature fluctuations, virus genotype, and initial viral load. Once a mosquito becomes infectious, it retains the capacity to transmit the virus throughout its lifespan.
Human-to-Mosquito Transmission
Infected individuals, whether symptomatic, pre-symptomatic, or asymptomatic, can transmit the dengue virus to mosquitoes. Transmission can occur up to 2 days prior to symptom onset and persists for up to 2 days post-resolution of fever. High viremia and elevated fever in the patient correlate with increased mosquito infection risk, whereas high levels of dengue virus-specific antibodies are associated with reduced risk.
Typically, viremia lasts for about 4–5 days but may extend up to 12 days. Maternal transmission of dengue from an infected mother to her newborn, while rare, is documented. The risk of vertical transmission appears to be influenced by the timing of maternal infection during pregnancy. Neonates born to infected mothers may experience pre-term delivery, low birth weight, and fetal distress.
Other Transmission Routes
Transmission via blood products, organ donations, and transfusions has been occasionally recorded. Additionally, transovarial transmission of the virus within mosquitoes has been observed.
Risk Factors and Environmental Influences
Previous dengue infection significantly increases the likelihood of developing severe dengue. Urbanization, particularly when unplanned, exacerbates dengue transmission through various social and environmental factors, including population density, human mobility, and water management practices. Community awareness and engagement in vector control are crucial for enhancing resilience against dengue.
The interplay between dengue virus, host, and environment is dynamic and influenced by climate change, urban expansion, and population movements. This complexity means that disease risks are likely to evolve, necessitating ongoing vigilance and adaptive strategies.
