Half of the world’s population is now at risk of dengue

Dengue (break-bone fever) is a viral infection that spreads from mosquitoes to people. It is more common in tropical and subtropical climates.

Most people who get dengue won’t have symptoms. But for those that do, the most common symptoms are high fever, headache, body aches, nausea and rash. Most will also get better in 1–2 weeks. Some people develop severe dengue and need care in a hospital.

Key facts about Dengue

• Dengue is a viral infection caused by the dengue virus (DENV), transmitted to humans through the bite of infected mosquitoes.
• About half of the world’s population is now at risk of dengue with an estimated 100–400 million infections occurring each year.
• Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.
• While many DENV infections are asymptomatic or produce only mild illness, DENV can occasionally cause more severe cases, and even death.
• Prevention and control of dengue depend on vector control. There is no specific treatment for dengue/severe dengue, and early detection and access to proper medical care greatly lower fatality rates of severe dengue.

Symptoms of Dengue

Most people with dengue have mild or no symptoms and will get better in 1–2 weeks. Rarely, dengue can be severe and lead to death.

If symptoms occur, they usually begin 4–10 days after infection and last for 2–7 days. Symptoms may include:

• high fever (40°C/104°F)
• severe headache
• pain behind the eyes
• muscle and joint pains
• nausea
• vomiting
• swollen glands
• rash.

Individuals who are infected for the second time are at greater risk of severe dengue.

Severe dengue symptoms often come after the fever has gone away:

• severe abdominal pain
• persistent vomiting
• rapid breathing
• bleeding gums or nose
• fatigue
• restlessness
• blood in vomit or stool
• being very thirsty
• pale and cold skin
• feeling weak.

People with these severe symptoms should get care right away.

After recovery, people who have had dengue may feel tired for several weeks.

Diagnostics and treatment of Dengue

Most cases of dengue fever can be treated at home with pain medicine. Preventing mosquito bites is the best way to avoid getting dengue.

There is no specific treatment for dengue. The focus is on treating pain symptoms.

Acetaminophen (paracetamol) is often used to control pain. Non-steroidal anti-inflammatory drugs like ibuprofen and aspirin are avoided as they can increase the risk of bleeding.

There is a vaccine called Dengvaxia for people who have had dengue at least once and live in places where the disease is common.

For people with severe dengue, hospitalization is often needed.

Global burden of Dengue

The disease is now endemic in more than 100 countries in the WHO Regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. The Americas, South-East Asia and Western Pacific regions are the most seriously affected, with Asia representing around 70% of the global disease burden.

Dengue is spreading to new areas including Europe, and explosive outbreaks are occurring. Local transmission was reported for the first time in France and Croatia in 2010 and imported cases were detected in 3 other European countries.

The largest number of dengue cases ever reported globally was in 2019. All regions were affected, and dengue transmission was recorded in Afghanistan for the first time. The American Region reported 3.1 million cases, with more than 25 000 classified as severe. A high number of cases were reported in Bangladesh (101 000), Malaysia (131 000) Philippines (420 000), Vietnam (320 000) in Asia.

Dengue continues to affect Brazil, Colombia, the Cook Islands, Fiji, India, Kenya, Paraguay, Peru, the Philippines, the Reunion Islands and Vietnam as of 2021.

Transmission of Dengue

Transmission through the mosquito bite

The virus is transmitted to humans through the bites of infected female mosquitoes, primarily the Aedes aegypti mosquito. Other species within the Aedes genus can also act as vectors, but their contribution is secondary to Aedes aegypti.

Human-to-mosquito transmission

Human-to-mosquito transmission can occur up to 2 days before someone shows symptoms of the illness, and up to 2 days after the fever has resolved.

Maternal transmission

The primary mode of transmission of DENV between humans involves mosquito vectors. There is evidence however, of the possibility of maternal transmission (from a pregnant mother to her baby).

Other transmission modes

Rare cases of transmission via blood products, organ donation and transfusions have been recorded. Similarly, transovarial transmission of the virus within mosquitoes have also been recorded.

Risk factors of Dengue

Previous infection with DENV increases the risk of the individual developing severe dengue.

Urbanization (especially unplanned), is associated with dengue transmission through multiple social and environmental factors: population density, human mobility, access to reliable water source, water storage practice etc.

Community’s risks to dengue also depend on population’s knowledge, attitude and practice towards dengue, as well as the implementation of routine sustainable vector control activities in the community.

Consequently, disease risks may change and shift with climate change in tropical and subtropical areas, and vectors might adapt to new environment and climate.

Prevention and control of Dengue

The mosquitoes that spread dengue are active during the day.

Lower the risk of getting dengue by protecting yourself from mosquito bites by using:

• clothes that cover as much of your body as possible
• mosquito nets if sleeping during the day, ideally nets sprayed with insect repellent
• window screens
• mosquito repellents (containing DEET, Picaridin or IR3535)
• coils and vaporizers.

If you get dengue, it’s important to:

• rest
• drink plenty of liquids
• use acetaminophen (paracetamol) for pain
• avoid non-steroidal anti-inflammatory drugs, like ibuprofen and aspirin
• watch for severe symptoms and contact your doctor as soon as possible if you notice any.

So far one vaccine (Dengvaxia) has been approved and licensed in some countries. However, only persons with evidence of past dengue infection can be protected by this vaccine. Several additional dengue vaccine candidates are under evaluation.

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