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Dengue fever

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Dengue fever is a viral disease caused by the dengue virus (DENV).

Dengue
Dengue

It is classified as a neglected tropical disease because it affects many people in specific regions. The virus belongs to the Flavivirus genus, which includes other viruses like Zika and West Nile.

Course of Dengue illness vectorized
Course of Dengue illness vectorized

Most cases of dengue are either asymptomatic or manifest only mild symptoms. However, a small portion of patients develop severe dengue, which can be life-threatening. This disease is a major global health concern because it is spreading to new areas.

dengue incidence, World, 2021
dengue incidence, World, 2021

The infection process begins with the bite of an infected female mosquito.

Aedes aegypti feeding
Aedes aegypti feeding

Primarily, the Aedes aegypti mosquito spreads the virus to humans. When a mosquito bites an infected person, it ingests the virus during a blood meal. The virus then replicates in the mosquito's gut cells. It eventually moves to the mosquito's salivary glands. When that mosquito bites a new person, it injects infectious saliva into the skin. The virus then infects skin cells called keratinocytes and specialized immune cells called Langerhans cells. These cells carry the virus to the lymph nodes. From there, the virus spreads through white blood cells throughout the entire body.

An infection typically follows three distinct phases: the febrile, critical, and recovery phases. During the febrile phase, patients experience a high fever between 40 and 41 degrees Celsius. This phase usually lasts between two and seven days. It is often accompanied by headaches, muscle pains, and joint pains. The critical phase follows and is where severe dengue can develop. In this stage, plasma may leak from the blood vessels. This leakage can lead to fluid accumulation in the lungs or abdomen. Finally, the recovery phase lasts about two to three days. During recovery, patients may experience striking improvement but might also feel severe itching.

There are four confirmed serotypes of the dengue virus, known as DENV-1, DENV-2, DENV-3, and DENV-4. These types are distinguished by their antigenicity, or how the immune system recognizes them. If you are infected with one serotype, you gain lifelong immunity to that specific type. However, you only gain short-term immunity to the other three types. This creates a risk called antibody-dependent enhancement, or ADE.

antibody dependent enhancement
antibody dependent enhancement

In ADE, the antibodies from a previous infection do not neutralize the new virus. Instead, they help the new virus infect immune cells more easily. This process significantly increases the risk of developing severe complications during a second infection.

Human understanding of dengue has changed significantly over the centuries. The earliest descriptions of a dengue outbreak date back to 1779. For a long time, the specific cause of the sickness remained a mystery. It was not until the early 20th century that scientists understood the viral cause and how it spreads. Today, we see the disease moving beyond traditional tropical zones. It is now appearing in the Iberian Peninsula and the southern United States. Scientists attribute this expansion partly to the effects of climate change on mosquito habitats.

The scale of the dengue epidemic is massive. During 2023, more than 5 million infections were reported worldwide. This resulted in more than 5,000 documented deaths. Because many cases are mild or show no symptoms, the actual numbers are likely under-reported. Severe dengue is a medical emergency that can cause organ failure. It can also lead to a reduction in platelets, which are necessary for blood clotting. This reduction increases the risk of bleeding from the gums, nose, or even internally.

Dengue fever symptoms
Dengue fever symptoms

Medical professionals use several tools to manage and prevent the disease. There is no specific treatment to cure the virus itself. Instead, treatment is symptomatic, focusing on managing pain and providing fluids. In severe cases, patients require hospitalization for intravenous fluids to maintain blood pressure. Doctors use blood tests to detect viral RNA or specific antibodies to confirm a diagnosis.

Dengue testing
Dengue testing

Prevention relies heavily on mosquito control and avoiding bites. Vaccines are also available to help. Dengvaxia was approved in 2016 for those previously infected. The Qdenga vaccine became available in 2022 for children and adults.

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File:Dengue fever symptoms.svg
Dengue fever symptoms.svg
File:Course of Dengue illness vectorized.svg
Course of Dengue illness vectorized.svg
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Dengue.jpg
File:Aedes aegypti feeding.jpg
Aedes aegypti feeding.jpg
File:antibody dependent enhancement.svg
antibody dependent enhancement.svg
File:Dengue testing.png
Dengue testing.png
File:Vector Control.jpg
Vector Control.jpg
File:Church of the Immaculate Conception, JB (2025) - img 10.jpg
Church of the Immaculate Conception, JB...
File:Intradermal injection.jpg
Intradermal injection.jpg
File:Dengue-fever-deaths,World,2021.svg
Dengue-fever-deaths,World,2021.svg
File:dengue incidence, World, 2021.svg
dengue incidence, World, 2021.svg

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