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The cases of dengue are on the rise in India. Recently, around 124 cases of dengue have been reported in Delhi since the beginning of the year 2021. In other cities like Faridabad, a total of nine dengue cases have been detected since the beginning of the year, while Ahmedabad has observed a surge of 168 per cent in cases of dengue.
Dengue is a mosquito-borne viral infection caused by the dengue virus (DENV) and transmitted through mosquitoes that belong to the Aedes species such as Aedes aegypti and Aedes albopictus. These mosquitoes are also known to cause chikungunya and Zika.
According to CDC, around 0.4 billion people globally get infected with dengue every year while the WHO says that more than 2.5 billion people worldwide, especially children of tropical and subtropical countries are at the risk of dengue. Also, a study published in the journal Nature Public Health Emergency Collection says that dengue is endemic in more than 140 countries in the USA, Asia, Africa and Eastern Mediterranean. 
In this article, we will discuss all about dengue such as its causes, symptoms, treatments and other details.
Types Of Dengue
Dengue is caused by the dengue virus that belongs to the Flaviviridae family and genus flavivirus. There are four distinct serotypes of the virus that mainly cause dengue: DENV-1, DENV-2, DENV-3 and DENV-4. This is the reason why in a lifetime, a person can possibly get dengue a maximum of four times. 
According to a study, the four serotypes of dengue are believed to have evolved from sylvatic DEN strains (transmission of the virus between non-human primates like monkeys and mosquito species of the forest) in the forests of Malaysia and West Africa. The time of evolution is estimated to be between 100 to 1500 years ago. 
How Is Dengue Virus Transmitted?
The transmission of dengue peaks during the rainy season and in areas where the temperature is low and humidity is high.  All the serotypes of the virus are known to cause a full spectrum of the disease.
Some of the ways by which the transmission of the virus to humans occurs:
1. Mosquito to human
The female Aedes mosquitoes are the ones that require a blood meal to produce eggs. They bite a dengue infected person and become the carrier of the virus. Inside their bodies, the virus replicates within 8-12 days and get disseminated to body tissues like salivary glands.
Then, when these infected mosquitoes bite another healthy individual, the virus gets transmitted to their bloodstream, resulting in dengue infection.
Remember: Once a person recovers from dengue infection, they become lifelong immune against the dengue serotype that has caused the infection. However, the person still can get infected by the remaining serotypes of dengue. Also, if coinfection by any of the remaining three serotypes occurs in a short duration after recovery from one serotype, the person could be at greater risk of developing severe dengue. 
2. Other ways of transmission
These include: 
- Infected needles.
- Receipt of infected blood.
- Transplacental infection from pregnant mother to newborn.
- Organ or tissue transplantation.
Symptoms Of Dengue
The incubation period of dengue is 4-8 days, after which the symptoms of the infection surface. They can range from asymptomatic to mild fever and from dengue fever to severe forms like dengue haemorrhage fever.
People with mild symptoms usually recover in 10 days. The mild symptoms of dengue are flu-like and include: 
- Sudden high fever of approximately 40 degree-Celcius.
- Vomiting and nausea
- Sore throat
- Muscle, bone and joint pain
- Swollen glands
- Pain behind the eyes
- Plasma leakage (dengue haemorrhage fever) 
- Bleeding from the gums and nose
- Continued vomiting
- Dengue shock syndrome
- Difficulty in breathing
- Severe abdominal pain
- Blood in the urine
- Irritability or restlessness
- Geography: Living or travelling to tropical areas like Southeast Asia, The Caribbean Islands, Africa, The Indian Subcontinent, etc.
- Age: Children below 3-4 years and elders are at higher risk. 
- Previous infection:Previous infection with one serotype of the dengue virus can increase the risk of coinfection with another serotype.
- Chronic diseases: Certain chronic conditions like diabetes mellitus, asthma, sickle cell anaemia and peptic ulcer. 
- Gene: Genetic background of the host. 
The severe warning signs of dengue include:
Risk Factors Of Dengue
Complications Of Dengue
Untreated or severe dengue can cause complications like: 
- Encephalitis and encephalopathy.
- Multiple organ failure.
- Virological test: It includes tests like reverse transcriptase-polymerase chain reaction (RT-PCR) to detect elements of the virus. 
- Serological test: It includes tests like enzyme-linked immunosorbent assays (ELISA) to detect antibodies produced in response to the dengue virus.
Diagnosis Of Dengue
Diagnosing dengue fever is difficult because the signs and symptoms are often the same as other diseases like malaria, typhoid fever and leptospirosis.
Some of the diagnostic methods for dengue include:
Note: These tests give appropriate results if done within the first week of the infection.
Treatment Of Dengue
There is no specific treatment for dengue fever. The condition is managed by supportive care depending on the criticality of the ongoing symptom, followed by continuous monitoring of the condition.
Some of these treatment methods include: 
- Fluid infusion: Either intravenously or drinking directly through the mouth to prevent dehydration and flush out the dengue virus from the system. Fluids like clean bottled water, soups, fresh fruit juices, and saline water are recommended.
- Transfusion of blood products: to supply fresh frozen plasma to increase the platelets count in the body.
- Nasal CPAP: To improve signs of acute respiratory failure.
- Medications: Like corticosteroids and Carbazochrome sodium sulfonate.
- LAV can stimulate neutralising antibodies against the dengue virus, but still lacks the ability to neutralise the DENV2 virus.
- Compared to LAV, RSV can trigger a balanced immune response against all four types of dengue serotypes, but cause problems related to improper protein folding which may lead to some diseases.
- VVV can produce potent cellular and humoral immunity in the neonatal mice body, but low in adult mice body
- DNA vaccines are cost-effective, stable and can easily be mass-produced, but have low immunogenicity.
Vaccines For Dengue
According to a study published in the journal Vaccines on 2 Feb 2020, there are currently five vaccine types available against dengue. These include live attenuated vaccine (LAV), DNA vaccine, inactivated vaccine (IV), viral vectored vaccine (VVV) and a recombinant subunit vaccine (RSV). 
However, each of them is still under the clinical trial phase and has some or other downsides.
Studies are taking place to develop the vaccine type that can provide high immunogenicity, is highly stable, have low-cost production and can provide a broad range of immunity.
How To Prevent Dengue?
- Dispose of solid waste properly.
- Cover, empty and clean domestic water storage containers on a weekly basis.
- Use insecticides in containers that hold standing water.
- Use mosquito repellents
- Wear full-sleeved clothes indoors and outdoors.
- Use mosquito nets while sleeping.
- Try to avoid staying outdoors at dawn, dusk and early evening
- Drink plenty of water.
- Take sufficient rest.
- Consult a medical expert if symptoms get worse.
Dengue is fatal only in a few cases, as most people get recovered within a week. However, if you notice severe symptoms or previously had dengue, it is good to consult a medical expert soon for early treatments.
According to experts, dengue is best treated with supportive care as there are no specific treatment methods available. Some of the supportive care methods include drinking a lot of water, taking proper rest and certain medications to reduce the symptoms like headache and fever.
According to the CDC, death due to dengue occurs in around 22000 cases out of 100 million people. This ratio says that dengue can be fatal only in very few cases. Also, there are four dengue virus serotypes that affect people, which means that a person can be infected with dengue only four times in a lifetime.
Dengue, in the severe stage, can affect multiple organs such as the liver, kidney, gums, respiratory system, eyes and brain. However, not all people infected with the dengue virus experience multiple organs failures. Many factors cause the severity of dengue in people such as age and genetics