Basic facts
- Dengue fever is a viral infection that is transmitted to humans when they are exposed to the bite of infected mosquitoes.
- Almost half of the world's population is now at risk of dengue fever, and it is estimated that between 100 and 400 million cases of infection occur annually.
- Dengue fever occurs in tropical and subtropical climates in the world, particularly in urban and peri-urban areas.
- Although many dengue infections are asymptomatic or cause only mild illness, the disease virus can sometimes cause more severe cases and even death.
- Dengue prevention and control depend on controlling its vectors. There is no specific treatment for dengue fever/severe dengue fever, but early detection of infection and access to necessary medical care significantly reduce the fatality rates resulting from severe dengue fever.
Overview
Dengue (bone-painful fever) is a viral infection transmitted to humans by mosquitoes and is most common in tropical and subtropical climates.
Most people who become infected with dengue fever do not have any symptoms, but the most common symptoms among those who do have it are high fever, headache, body aches, nausea, and skin rash. The health condition of most of these patients improves within a period of one to two weeks.
Dengue fever can cause death in severe cases.
You can reduce your risk of dengue fever by avoiding mosquito bites, especially during the day.
Dengue fever is treated with painkillers because there is currently no specific treatment for it.
Symptoms of the disease
Most people infected with dengue fever have mild symptoms or no symptoms at all, and their health improves within one to two weeks. In rare cases, dengue fever may be severe and cause death.
If symptoms are present, they usually begin 4 to 10 days after infection and last for 2 to 7 days. Symptoms of the disease may include:
- High fever (40°C/104°F)
- Severe headache
- Pain behind the eye sockets
- Muscle and joint pain
- Nausea
- Vomiting
- Swollen glands
- Skin rash.
Individuals with a second infection are at greater risk of developing severe dengue fever.
Symptoms of severe dengue often appear after the fever has subsided, and include the following:
- Severe abdominal pain
- Constant vomiting
- Rapid breathing
- Bleeding gums or nose
- Exhaustion
- Fidgeting
- The presence of blood in the vomit or stool
- Feeling very thirsty
- Pale and cold skin
- Feeling weak.
People who exhibit these severe symptoms should seek care immediately.
People with dengue fever may feel tired for several weeks after recovering from the disease.
Methods of diagnosing and treating the disease
There is no specific treatment for dengue fever, and the focus is on treating the pain symptoms only, knowing that most cases of dengue fever can be treated at home using painkillers.
Acetaminophen (paracetamol) is often used to relieve pain. The use of nonsteroidal anti-inflammatory drugs such as ibuprofen and aspirin should be avoided because they can increase the risk of bleeding.
People with severe dengue fever need to be hospitalized in most cases.
Global burden of disease
The incidence of dengue fever has increased sharply worldwide in recent decades, with the number of cases reported to WHO rising from 430,505 in 2000 to 5.2 million in 2019. Most cases of dengue are asymptomatic or mild and managed Self-reported, the rate of reporting the actual number of cases of infection is lower. Many of its cases are also misdiagnosed as other febrile illnesses (1) .
The year 2023 witnessed the largest number of dengue fever cases recorded, affecting more than 80 countries located in all WHO regions. Since the beginning of 2023, ongoing transmission combined with a sudden and unexpected rise in dengue cases has led to a historic increase in cases exceeding 6.5 million cases and more than 7,300 dengue deaths reported.
The following are several factors behind the increased risk of a dengue pandemic: Changes in the distribution of vectors (most notably Aedes aegypti and Aedes albopictus mosquitoes), especially in countries where dengue has not previously occurred; The consequences of the El Niño phenomenon in 2023 and climate change, causing higher temperatures and increased rates of precipitation and humidity; the fragility of health systems in response to the COVID-19 pandemic; The lack of political and financial stability in countries facing complex humanitarian crises and increasing rates of population movement.
One modeling estimate indicates that 390 million dengue virus infections occur annually, of which 96 million are accompanied by clear clinical symptoms (2) . Another study, which estimates the prevalence of dengue fever, indicates that there are 3.9 billion people at risk of infection with dengue viruses (3) .
The disease has now become endemic in more than 100 countries located in the African Region, the Americas Region, the Eastern Mediterranean Region, the Southeast Asia Region and the Western Pacific Region of the Organization, noting that the regions of the Americas, Southeast Asia and the Western Pacific are most affected by the disease. Asia suffers from 70% of its global burden.
The spread of dengue fever extends to new areas in Europe, the Eastern Mediterranean, and South America.
The largest number of dengue fever cases was reported in 2023, with the WHO Region of the Americas reporting 4.5 million cases and 2,300 deaths. A large number of cases of the disease have also been reported in Asia as follows: Bangladesh (321,000 cases), Malaysia (111,400 cases), Thailand (150,000 cases) and Viet Nam (369,000 cases).
Disease transmission
Transmission of the disease by mosquito bite
Dengue virus is transmitted to humans by biting infected female mosquitoes, mainly of the Aedes aegypti species. There are other species of Aedes mosquitoes that can also serve as vectors of the disease, but their contribution to transmitting it is secondary compared to Aedes aegypti. But in 2023, Europe saw a sudden increase in local transmission of dengue fever by Aedes albopictus (tiger mosquitoes).
After the mosquito feeds on the blood of an infected person, the virus multiplies in its middle stomach before spreading to its secondary tissues, including the salivary glands. The time it takes for a mosquito to ingest the virus until it actually transmits it to a new host is called the external incubation period. This period takes approximately 8 to 12 days when the ocean temperature ranges between 25 and 28 degrees Celsius. Differences in external incubation are not only affected by ambient temperature; Rather, there are many factors affected by it, such as the magnitude of daily temperature fluctuations, the genotype of the virus, and initial virus concentrations, which can also change the time it takes the mosquito to transmit it. Once a mosquito becomes infectious, it can transmit the virus for the remainder of its life .
Transmission of the disease from humans to mosquitoes
Mosquitoes can become infected with dengue fever from people who carry the virus in their blood. These can be people who have symptomatic dengue infection, those who have not yet developed symptoms, or other people who show no signs of illness (asymptomatic infection).
The infection can be transmitted from humans to mosquitoes up to two days before a person shows symptoms of illness, and up to two days after his or her fever subsides.
The possibility of a mosquito infecting the disease increases with the increase in the presence of viruses in the patient’s blood and the increase in his body temperature. Otherwise, higher levels of antibodies to dengue virus specifically in the blood are associated with a lower likelihood of a mosquito becoming infected with the disease. The virus remains in the blood of most people for between 4 and 5 days, but its survival may last up to 12 days.
Transmission of the disease from mother to child
The main mode of transmission of dengue virus between humans is through its mosquito vectors. However, there is evidence that the virus can be transmitted from the mother (the pregnant woman to her child). At the same time, rates of mother-to-child transmission of the virus appear to be low, given that the risks of transmission in this way appear to be related to the timing of dengue infection during pregnancy. If the mother does become infected with dengue fever during pregnancy, her baby may be born prematurely and may suffer from low birth weight and fetal distress.
Other methods of disease transmission
Rare cases of transmission through blood products, organ donation and blood transfusion have been reported. Cases of transmission of the virus via the ovarian route in mosquitoes have also been recorded.
Disease risk factors
Previous exposure to dengue fever increases an individual's risk of developing severe dengue infection.
Urban expansion (particularly unregulated) is associated with dengue transmission through several social and environmental factors: population density, human mobility, availability of a reliable water supply, water storage practice, etc.
The risk of a community being exposed to dengue fever also depends on the extent of residents' knowledge, attitudes and practices towards dengue fever, because exposure to the disease is closely linked to behaviors such as storing water, raising plants, and protecting oneself from mosquito bites. Community resilience is greatly enhanced by their participation in routine vector surveillance and control activities.
Vectors may adapt to new environmental and climate conditions due to the dynamic nature of the interaction between dengue virus, host and environment. Therefore, disease risks can change and change in light of climate change in tropical and subtropical regions, in conjunction with increasing rates of urbanization and population movements.
Disease prevention and control
The mosquitoes that spread dengue fever are active during the day.
Reduce your risk of dengue fever by protecting yourself from mosquito bites by doing the following:
- Wear clothes that cover as much of your body as possible
- Sleeping during the day under mosquito nets that prevent mosquitoes from entering, and it is advisable to spray mosquito nets with insect repellent materials.
- Installing screens on windows
- Use mosquito repellent products (containing DEET, Picaridin, or IR3535)
- And the use of coils and vaporizers.
Mosquito breeding can be prevented by doing the following:
- Prevent mosquitoes from accessing egg-laying habitats by managing and modifying the environment;
- Proper disposal of solid waste and removal of man-made habitats that can retain water;
- Cover, empty, and clean household water storage containers weekly;
- Lubricate outdoor water storage containers with appropriate insecticide.
If you have dengue fever, it is necessary to do the following:
- Get some rest
- And drink large amounts of fluids
- Use acetaminophen (paracetamol) to relieve pain
- Avoid nonsteroidal anti-inflammatory drugs, such as ibuprofen and aspirin
- Monitor for severe symptoms and contact your doctor as soon as possible if you notice any of them.
One vaccine (QDenga) has been approved and licensed in some countries so far, but it is only recommended for use in people aged 6 to 16 years in settings with high transmission rates. Several additional vaccines against the disease are also currently being evaluated.