Dengue Fever

M.Khalid October 1, 2022May 26, 2023

Last Update on October 30, 202

1. What is Dengue Fever?

Dengue fever viruses are transmitted to humans by biting infected Aedes species mosquito. The Aedes species mosquito is called Ae. aegypti or Ae. albopictus). Female mosquitoes, primarily of the type Aedes aegypti and, to a lesser extent, Ae, carry the dengue fever virus. albopictus. These mosquitoes are capable of spreading the chikungunya, zika, and yellow fever viruses. Local socioeconomic, environmental, and climate factors—both of which are prevalent in the tropics affect dengue fever risk differently depending on where you live.

Approximately 4 billion people live in locations where dengue fever is a possibility or close to half of the world’s population. In regions where there is a danger, dengue fever is frequently the most common sickness.

Dengue fever affects up to 400 million people annually. A hundred million people worldwide develop an infection, and severe dengue causes 40,000 fatalities.

One of the four closely related dengue viruses such as dengue viruses 1, 2, 3, and 4—causes the disease. As a result, a person has a chance of getting dengue fever up to four times in their lifetime.

A wide range of diseases is caused by the dengue virus. This can range from minor flu-like symptoms to serious diseases in sick patients. Even though it happens less frequently, severe dengue fever can still cause serious bleeding, organ damage, and/or plasma leakage in some individuals. There is a higher chance of death when dengue virus disease in humans is not treated properly

2. Types of Dengue fever viruses:

There are four different but closely related serotypes of the Flaviviridae family virus that causes dengue fever, which is the primary cause of illness.

DENV-1
DENV-2
DENV-3
DENV-4

Antibodies against that serotype are thought to last a lifetime following infection recovery. Following recovery, cross-immunity to the other serotypes is only temporary and incomplete. Subsequent infections (secondary infection) caused by different serotypes raise the likelihood that severe dengue fever.

There are 4 different sub-types of the dengue virus. Each type has its own particular epidemiological mechanism. All four serotypes are hyper-endemic in many countries, and they can co-circulate within a given area. Both human health in the world and national economies are adversely impacted by dengue. Infected visitors frequently bring DENV from one location to another; if responsive vectors are found in these new regions, there is a possibility for local infection to be developed.

3. Transmission of dengue fever:

There are different ways to transfer dengue fever

Transmission through the mosquito bite
Human-to-mosquito transmission
Maternal transmission

3.1. Transmission through mosquito bite:

The virus spreads to people when infected female mosquitoes, generally the Aedes aegypti mosquito, bite them. Even if there are other Aedes genus species that can serve as vectors, Aedes aegypti is the main source of transmission.

After feeding on a host that has DENV infection, the virus reproduces in the mosquito’s midget before spreading to auxiliary tissues like the salivary glands. The extrinsic incubation period refers to the amount of time between consuming the virus and actually transmitting it to a new host (EIP). When the outside temperature is between 25 and 28 °C, the EIP takes approximately 8 to 12 days.

The number of daily temperature fluctuations, the virus genotype, and the initial viral concentration is a few other variables that might affect the extrinsic incubation period and hence the length of time it takes for a mosquito to transmit a virus. After getting an infection, the mosquito can carry viruses for the entire duration of its life.

3.2. Human-to-mosquito transmission:

The DENV virus can be spread to mosquitoes by people who have the virus. This can include persons who have symptoms of dengue fever, those who are pre-symptomatic but have not yet developed symptoms, as well as those who are completely well (they are asymptomatic)

Up to 2 days, before someone exhibits symptoms of the sickness and up to 2 days after the fever has subsided, the human-to-mosquito transfer can happen.

High levels of DENV-specific antibodies are linked to a reduced risk of mosquito disease, whereas high levels of viremia and fever in the patient are positively correlated with the chance of mosquito infection (Nguyen et al. 2013 PNAS). Although viremia can persist for up to 12 days, most patients are viremic for about 4–5 days.

3.3. Maternal transmission:

The primary mechanism of DENV infection between people is through mosquito species. However, there is proof that maternal transfer could occur (from a pregnant mother to her baby). Although the risk of vertical transmission appears to be associated with the timing of the dengue fever during pregnancy, vertical transmission rates appear to be minimal. Babies may have a preterm delivery, low birth weight, and fetal distress when a mother has a DENV infection while she is pregnant.

3.4. Other transmission ways:

There have been a few recorded examples of transmission by blood products, organ donation, and transplants. Similar to this, there are records of the virus being transmitted transovarially within mosquitoes.

4. Causes of Dengue Fever:

The main DENV vector is thought to be the Aedes aegypti mosquito. It could reproduce in naturally occurring containers like tree holes and bromeliads, but today it has become well adapted to urban habitats and primarily reproduces in man-made containers like buckets, mud pots, abandoned containers, used tires, storm water drains, etc., making dengue fever a sneaky illness in densely populated urban centers.

Ae. aegypti feeds during the day; its peak biting times are in the early morning and just before dusk in the evening [19] Female Ae. Aedes aegypti repeatedly feeds between each egg-laying session, causing groups of infected people. After the female lays her eggs, they can remain dry for many months before hatching when they are placed in water.

Aedes albopictus, a secondary dengue vector, has spread to more than 25 nations in Europe and more than 32 states in the United States, partly as a result of global commerce in old tires, which serve as a breeding ground for the insect (e.g. lucky bamboo).

Although it is believed to be strongly developed in cities, it likes breeding grounds in regions of dense vegetation, especially plantations. Dengue fever raises the danger of exposure for workers in rural areas, notably those in rubber and palm oil plantations. Ae. The albopictus is very adaptable.

5. Signs and symptoms of Dengue Fever:

Dengue fever can emerge as a serious, flu-like sickness that affects newborns, young children, and adults but seldom results in death, even though the majority of patients are asymptomatic or present minor symptoms. Symptoms normally linger for 2–7 days after the initial infection or 4–10 days that followed the bite of an infected mosquito.

Dengue fever is divided into two major types by the World Health Organization:

Dengue fever
Severe dengue fever

In order to prioritize patients for hospital admission, ensure proper monitoring and lower the risk of getting the more severe dengue fever. Medical experts use the sub-category of dengue with or without warning signals.

5.1. Dengue Fever:

When a high fever (40°C/104°F) is followed by two of the following symptoms during the febrile phase (2–7 days), dengue should be considered:

Severe headache
High Fever
Pain behind the eyes
Muscle and joint pains
Nausea
Vomiting
Swollen glands
Rash.

5.2. Severe Dengue Fever:

A patient often reaches the crucial period 3–7 days after the start of their disease. A small percentage of patients may experience a dramatic increase in symptoms during the essential phase’s first 24 to 48 hours.

The warning signals of severe dengue fever can appear at this point when the patient’s temperature is dipping (below 38°C/100°F). Due to plasma leakage, fluid storage, respiratory difficulties, severe bleeding, or organ dysfunction, severe dengue fever is a potentially deadly consequence.

Doctors should keep an eye out for the following early symptoms:

Severe abdominal pain
Persistent vomiting
Rapid breathing
High Fever
Bleeding gums or nose
Fatigue
Restlessness
Liver enlargement
Blood in vomit or stool.

If patients show these symptoms during the critical period, close monitoring is required for the ensuing 24-48 hours in order to provide the required medical care, lower consequences, and lower the risk of death. Continued careful monitoring should also be done during the convalescent phase.

6. Diagnose Dengue Fever:

DENV infection can be identified by using a variety of techniques. Depending on when the patient first appears, different diagnostic procedures may be used, some more appropriate than others. Both of the following testing techniques should be used on patient samples obtained during the first week of disease:

Virus isolation methods
Serological methods

6.1. Virus isolation methods:

In the early stages of illness, the virus may be isolated from the blood. Reverse transcriptase-polymerase chain reaction (RT-PCR) techniques come in a variety and are thought to be the best. To execute these examinations, staff members need specialized tools and training.

The virus may also be found by looking for the NS1 protein, which is generated by viruses. For this, there are commercially marketed rapid diagnostic tests that can be used. The test results are ready in just 20 minutes, and it doesn’t call for any specific laboratory methods or tools.

6.2. Serological methods:

By detecting anti-dengue antibodies, serological techniques like enzyme-linked immunosorbent tests (ELISA) can determine whether a current or previous infection existed. IgM antibodies can be found around a week after infection and last for about three months. IgM indicates a recent DENV infection when it is present. The body retains IgG antibody levels for years and they take longer to develop. IgG indicates a prior infection because it is present.

7. Treatment of Dengue Fever:

Dengue fever has no specific therapy. Patients need to relax, hydrate well, and visit a specialist. Patients may be sent home, sent for in-hospital treatment, or need emergency care and an urgent transfer depending on the clinical symptoms and other factors.

To manage the symptoms of muscle aches and pains, fever, an approach for the development, such as painkillers and fever reducers, can be used.

Acetaminophen or paracetamol works well for treating these symptoms.

Ibuprofen and aspirin are examples of NSAIDs (non-steroidal anti-inflammatory medicines), which should be avoided. These anti-inflammatory medications work by thinning the blood, and blood thinners may make the prognosis worse in conditions where there is a danger of hemorrhage.

When treating severe dengue fever, doctors and nurses who are familiar with the symptoms and course of the illness can save lives and lower mortality rates to less than 1% in most countries.

8. Vaccination against Dengue Fever:

Dengvaxia® (CYD-TDV), the first dengue fever vaccine created by Sanofi Pasteur, was licensed in December 2015 and has now received regulatory approval in about 20 countries. The outcomes of an additional investigation to ascertain serostatus at the time of vaccination were made public in November 2017.

Study results showed that, in comparison to trial participants who were not vaccinated. The subset of trial participants who were inferred to be seronegative at the time of first vaccination had a higher risk of getting more severe dengue fever. Therefore, usage of the CYD-TDV vaccine is targeted at people aged 9 to 45 who have experienced at least one episode of dengue virus infection and who live in endemic areas. There are other dengue fever vaccine candidates being looked at.

Children aged 9 to 16 who have already experienced laboratory-confirmed dengue virus illness and reside in dengue-endemic areas are now allowed to use a new dengue fever vaccination (which occurs frequently or continuously). Some U.S. areas and states with free associations are considered endemic zones. Travelers from the United States who are visiting but not residing in a region where dengue fever is common are not eligible to use the vaccination.

An integrated dengue prevention and control strategy should take vaccination into account. Other disease prevention strategies, such as effective and persistent vector control, must be followed consistently. Whether or not they have had a vaccination, people should seek quick medical attention if dengue-like symptoms appear.

9. Risk factors of Dengue Fever:

The likelihood of someone having severe dengue fever is increased if they have previously been infected with DENV.

Through a variety of social and environmental factors, including population density, human mobility, availability of a dependable water source, water storage practices, etc., development (particularly unplanned urbanization) is linked to dengue transmission.

The population’s knowledge, attitude, and behavior about dengue fever as well as the implementation of regular sustainable vector control operations in the community all affect the community’s risks for the disease.

As a result, disease risks could vary and shift as a result of climate change in tropical and subtropical regions, and viruses may be able to adapt to the new environment.

10. Prevention and control of Dengue Fever:

Avoid further mosquito bites during the first week of your sickness if you already have dengue fever. Because the virus might be circulating in your blood at this time, you run the risk of spreading it to fresh, uninfected mosquitoes, which could then infect more individuals.

The existence of mosquito breeding places close to areas where people live is a major risk factor for dengue fever. The main method for controlling or preventing the transmission of the dengue virus at the time is the control of mosquito vectors. This is performed by:

Prevention and control of mosquito breeding:

Limiting mosquito access to places where they lay their eggs through environmental management and alteration;
Eliminating artificial dwellings constructed by humans that can hold water and safely dispose of solid waste;
Home water storage tanks must be covered, emptied, and cleaned on a weekly basis.
Applying the proper chemicals to outdoor water storage tanks
Protect yourself from mosquito bites:
Employing personal protective measures for the home, such as window screens, repellents, coils, and vaporizers.
These safeguards must be done both inside and outside of the home because the main mosquitoes attack throughout the day.
It is important to wear clothes that reduce skin exposure to mosquitoes.
Community engagement:
Educating people about the risk of dengue fever spread by mosquitoes.
Engaging the public to increase involvement and mobilization for long-term vector control.
Active mosquito & virus surveillance:
To ascertain the efficacy of control strategies, active monitoring and surveillance of vector abundance and species composition should be conducted;
Actively screen sentinel mosquito samples to continuously monitor viral transmission in the mosquito population;
Mosquito monitoring can be combined with clinical and environmental observation.

However, there is ongoing research being conducted by numerous multinational collaborations in the search for cutting-edge tools and creative tactics that will support international efforts to stop the spread of dengue fever. The WHO promotes the integration of vector management strategies to produce sustainable, productive local adaptations of vector control programs.