What Is Dengue Fever?

Overview

Dengue fever is a viral infection spread by mosquitoes. It largely affects public health in tropical regions of the world. In most cases, only mild symptoms are experienced and it gets better without any intervention but in some people, the illness can be severe and can even result in death. 

The prevalence of the illness may be higher than current research states because in many cases, the symptoms can be confused with other viral infections or the patient may be asymptomatic. Furthermore, dengue fever occurs in many poor regions of the world, meaning that they do not have the testing facilities available to confirm a diagnosis of dengue. 

Causes of dengue fever

Dengue fever is caused by the bite of infected mosquitoes belonging to the Aedes species; Aedes aegypti and Aedes albopictus. This species of mosquito also spread Zika and Chikungunya viruses. The dengue virus is a member of the Flaviviridae virus family found mostly in ticks and mosquitoes. They cause viral hemorrhagic fevers.  

Four different dengue viruses can be transmitted and so a person can have dengue fever up to 4 times. For each specific dengue virus, contracting it means that you will then be immune from catching that specific strain again.¹

Dengue fever can also be passed from a mother to her fetus. There’s only currently been a single case of dengue being transmitted to a child through breast milk and so breastfeeding is not considered a risky behaviour in areas in which dengue fever is common. It appears that the benefits of breastfeeding outweigh the risk of passing on the virus in this way.²

Controlling the vector (mosquitoes) is the best way to control the transmission of the virus and this can be achieved by reducing the risk of getting bitten by a mosquito and communities taking preventative measures to reduce the opportunity for mosquitoes to breed. 

Signs and symptoms of dengue fever

Only 1 in 4 people infected with the virus have symptoms.³

After being bitten by an infected mosquito, the incubation period is around 4-10 days.⁴

The majority of cases of dengue fever are mild. After the incubation period follows the febrile phase lasting roughly 2-7 days. Symptoms can include the following:⁵

• High fever
• Pain behind the eyes
• Muscle and joint aches
• Nausea and vomiting
• Swollen glands
• Rash 

There is a critical phase that occurs between days 3 and 7 of illness onset. The critical phase lasts around 24-48 hours; during this time a small number of patients rapidly deteriorate. 

Severe dengue affects around 1 in 20 of those infected. There are warning signs that develop a couple of days after the high fever has dissipated. These warning signs include the following:

• Persistent vomiting
• Stomach pain
• Bleeding from the nose and/or gums
• Blood in vomit or faeces 
• Fatigue
• Restlessness
• Feeling irritable
• Rapid breathing 

The risk of developing severe dengue is increased if you have had dengue fever previously.⁶ Severe dengue is a medical emergency because it can result in severe bleeding, organ failure, and respiratory distress. It’s important to seek professional help if you think that you may have developed this condition.⁷

Management and treatment for dengue fever

Mild symptoms can be dealt with at home with paracetamol and lots of fluids and rest. It’s important to prevent dehydration. You need extra fluids to account for the loss experienced as a result of vomiting. The NHS states that it is important to not take anti-inflammatory painkillers such as ibuprofen if you suspect you have dengue fever because they can cause bleeding. 

Remaining vigilant for the warning signs of severe dengue for 2 days after the fever has reduced is vital to be able to seek medical attention if needed. 

Preventing other people from catching dengue from you is essential. Although it cannot be passed on directly, should a mosquito bite you whilst you’re infected and then go on to bite somebody else, they may become infected. Using mosquito prevention methods such as wearing long clothes and using insect repellents will reduce the risk of another mosquito bite.⁸

FAQs

How is dengue fever diagnosed? 

If you have symptoms of dengue fever or live in/have recently travelled to a country in which dengue is common, your healthcare provider should carry out a blood test. This is the only way to confirm a diagnosis of dengue fever. 

Once the blood has been sent to the laboratory, a nucleic acid amplification test (NAAT) can detect the virus genetic material within the blood if it is present but only during the first 7 days of infection. After 7 days, the virus is harder to detect and so serologic tests need to be carried out on the blood sample; the blood will need to be analyzed for dengue-specific IgM antibodies that stick around for up to 12 weeks after infection with the virus.⁹

Can dengue fever be prevented? 

As dengue fever is caused by mosquito bites, avoiding them is the key to preventing dengue. The chances of being bitten by a mosquito can be reduced by:¹⁰

• Using insect repellent (The United States Environmental Protection Agency has a tool to help you find the most appropriate repellent for you)
• Use mosquito screens and nets
• Wear long sleeves and trousers when outside- remember that mosquitoes bite both during the day and night

Eliminating the areas in which mosquitoes lay their eggs also reduces the number of mosquitoes in your immediate surroundings. This is called source reduction. Habitats where dengue mosquitoes are likely to lay their eggs are vessels containing water both indoors and outdoors. These might include the following:

• Flower vases 
• Holes in construction sites
• Children’s play equipment
• Discarded bottles/packaging
• Old tyres
• Water storage tanks, including drinking water tanks
• Leaves
• Buckets
• Holes in trees
• Bogs and trenches

Covering vessels used to collect or store water prevents mosquitoes from getting inside them and so their eggs cannot be laid. Containers that cannot be covered should be thoroughly cleaned at least once a week to prevent the eggs from maturing to a stage where they hatch into mosquitoes.¹¹

Is dengue fever contagious? 

Dengue fever cannot be passed from person to person. However, if an infected person is bitten by a mosquito, this mosquito can then become infected and the disease can be passed on in this way; this explains how dengue fever can spread to other areas.¹²

How long does dengue fever last? 

Symptoms generally last for 2-7 days. After roughly a week most people will have recovered. 

Who are at risk of dengue fever? 

Almost half of the world’s population, that is 4 billion people are at risk of developing dengue fever. Anybody who lives in or travels to an area that is endemic for dengue is at risk of catching it. It is mostly an issue in tropical and subtropical regions, mostly in urban and semi-urban areas but it can occur anywhere that Aedes aegypti and Aedes albopictus mosquitoes live. 

Some of the areas where dengue is most common are:

• Southeast Asia
• Latin America
• Africa

There have also been cases in Europe and southern parts of America.¹³

How common is dengue fever? 

Because many cases of dengue fever are asymptomatic, there isn’t a definitive answer to the question of how common it is,  The World Health Organisation estimates that there are 390 million infections each year. 80% of these are mild. 

When should I see a doctor? 

If you have any symptoms of dengue fever you should contact your doctor right away. This is also the case if you develop symptoms and have travelled to an area within the past few weeks that is endemic for dengue. 

Summary

Dengue fever is a viral infection spread by the bite of mosquitoes belonging to the Aedes family. It occurs in many regions of the world, with half of the world’s population being at risk of developing it at some point. In most cases, the symptoms are mild and patients make a full recovery. 

However, in a small minority of cases, severe dengue can cause serious illness and even death. There is no specific treatment for dengue fever but the best way to prevent the virus is to lower the risk of being bitten by a mosquito.