Overview
Causes of Disease
- It is an infectious disease caused by a single-stranded, positive-RNA virus belonging to the Flaviviridae family, which is mainly concentrated in tropical and subtropical regions, exposing approximately one-third of the world's population to the risk of infection.
- There are four serotypes of the virus (DENVs 1-4) and they often circulate together in the same areas, and the dominant serotype can change over time due to outbreaks and population immune shifts.
- In the event of infection with one serotype, long-term protective immunity is stimulated only to the same serotype exposed to it and short-term protection (over only 3-6 months) to the other types, so it is possible for a person to be infected with dengue fever several times in his life.
Modes of Transmission:
- The disease is transmitted to humans primarily through the bite of infected female Aedes aegypti mosquitoes. Although a tropical mosquito, contemporary reports document its persistence outside these areas, as it thrives in urban areas, is closely associated with human habitation, and readily enters buildings for feeding and rest. It is highly efficient in transmission due to its strong human affinity and multiple bites.
- The Aedes albopictus mosquito (the Asian tiger mosquito) is a secondary tolerant vector of infection. Despite its low transmission efficiency, it poses an increasing threat as it spreads to temperate regions and becomes more prevalent in rural and semi-urban areas.
Symptoms and Signs
Dengue fever may take one of the following forms:
- Non-specific fever: represents the majority of cases and is often asymptomatic.
- Simple dengue: Characterized by fever with severe headache, joint and muscle pain, and skin rash.
- Dengue fever with warning signs: persistent vomiting, severe abdominal pain, low blood pressure, or bleeding in the mucous membranes and at injection sites. The risk of developing dengue hemorrhagic fever increases with repeated infection with another type of virus.
Treatment
- There is currently no specific antiviral treatment available for dengue infection. Treatment focuses primarily on symptom relief (particularly pain medication) and prevention of complications.
- Vaccine
- Two dengue vaccines have been licensed: Dengvaxia® (CYD-TDV) and Qdenga® (TAK-003).
- Another dengue vaccine, developed at the Infectious Diseases Laboratory of the National Institutes of Allergy and Infectious Diseases in the United States, is in the final stages of clinical development.
- Global Epidemiological Situation in 2024
Overview
- Since the beginning of 2024, more than 14 million dengue cases and more than 10,000 dengue-related deaths have been reported worldwide.
- There are 90 countries with active dengue transmission in 2024, not all of which are officially reported. In addition, many endemic countries do not have strong detection and reporting mechanisms, so the true burden of dengue worldwide is underestimated.
- The number of dengue cases reported worldwide has doubled each year since 2021, but this increase has been particularly pronounced in the Americas. 9
Pan American Health Organization (PAHO)
- Between epidemiological weeks 1 and 44 of 2024, a total of 12,479,437 suspected cases of dengue were reported (53% of which were laboratory confirmed), resulting in a cumulative incidence rate of 1,307 per 100,000 inhabitants, representing a 204% increase compared to the same period in 2023 and a 381% increase compared to the average of the past five years.
- 20,916 cases (0.17%) were classified as severe dengue and a total of 7,575 deaths were recorded. 10
- Brazil reported the highest number of cases in 2024 (over 9.8 million), followed by Argentina, Mexico, Colombia and Paraguay. .
- The French region of the Isles of the Vallees reported a weekly caseload of 540 cases until the end of October, more than double the number seen in September. The outbreak earlier this year was caused by DENV-2 serotype, while DENV-3 serotype has recently been detected in more than 90% of samples analyzed.
- There is a possibility of cases spreading to other areas due to extensive travel and migration.
Europe
- As of November 2024, locally transmitted dengue cases have been confirmed in France, Italy and Spain.
- The number of dengue cases in France has increased significantly: from May 1 (the beginning of the Asian tiger mosquito activity period) to October 18, 85 people were infected in France without having travelled to an endemic country.
- The number of locally transmitted cases in Italy has increased by 159.7% compared to last year, with a total of 213 cases in 2024.
Eastern Mediterranean Region
- Dengue outbreaks continue to occur in fragile, conflict-affected and/or at-risk countries in the region with weak health care systems.
- In Iran, less than 20 imported dengue cases were recorded annually before 2024, but this year 221 dengue cases were reported by the beginning of October13. Local cases of the disease were reported in Iran in June 2024 for the first time in history.
Southeast Asia
- In Bangladesh, the total number of dengue cases and deaths in 2024 remains lower than reported for the same period in 2023 (71,393 cases and 355 deaths in 2024 as of 10 November, compared to 291,791 cases and 1,476 deaths in 2023).
- In Nepal, 28,212 cases were reported through the Early Warning and Alert System in 2024, and the total case numbers are lower than the same period last year.