Dengue Fever: Causes, Symptoms and Treatment

Dengue fever is a viral illness spread by mosquitoes, mainly Aedes aegypti and Aedes albopictus, which are most active during the day. It causes symptoms similar to the flu but can develop into a serious and sometimes life-threatening condition. The virus has four closely related types (DENV-1 to DENV-4), so a person can catch dengue more than once.

The disease occurs in over 100 countries, especially in warm, humid regions of Southeast Asia, the Pacific Islands, the Caribbean, Africa, and the Americas. Each year, an estimated 100–400 million people are infected, with outbreaks often happening during rainy seasons when mosquitoes breed more easily. Typical symptoms include high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen lymph nodes, and a skin rash. Severe dengue, also called dengue haemorrhagic fever, can cause dangerous complications such as fluid loss from blood vessels, severe bleeding, organ damage, or shock, which can be fatal without urgent medical care.

There is no specific cure for dengue. Treatment focuses on relieving symptoms and preventing complications, usually through rest, drinking plenty of fluids, and taking paracetamol (acetaminophen) to reduce fever and pain. Medicines like ibuprofen and aspirin are avoided because they can increase bleeding risk. Severe cases may require hospital care, intravenous fluids, and close monitoring.

Prevention involves controlling mosquito populations and reducing the chance of bites. This includes removing standing water where mosquitoes breed, using insecticides, wearing protective clothing, applying mosquito repellent, and sleeping under treated bed nets. In some countries, a vaccine called Dengvaxia is available but is recommended only for people who have had dengue before, due to safety concerns.

Global Prevalence

Dengue fever is endemic in over 100 countries across Asia, the Americas, Africa, and the Pacific, placing nearly half of the world’s population at risk. The World Health Organization (WHO) estimates that around 390 million infections occur each year, with approximately 96 million cases presenting clinical symptoms ranging from mild fever to severe, life-threatening illness. In recent decades, the disease’s geographic range has expanded significantly, with cases now reported in parts of Europe and the United States where local transmission was previously absent.

Outbreaks are most common during the rainy season, when standing water provides abundant breeding sites for Aedes mosquitoes, the primary vectors. Urbanization, inadequate waste management, and globalization — particularly increased travel and trade — have accelerated the spread of dengue into densely populated urban centers and previously unaffected rural regions.

High-risk areas include Southeast Asia, Latin America, and parts of Africa, where Aedes aegypti and Aedes albopictus mosquitoes thrive in warm, humid climates. Climate change, with its influence on rainfall patterns and temperature, is expected to further increase the geographic reach of these vectors.

History and Discovery

The earliest recorded outbreak of dengue fever occurred between 1779 and 1780, affecting multiple continents including Asia, Africa, and North America. Historical accounts describe a sudden onset of high fever, severe joint and muscle pain, and rash, symptoms that earned the disease nicknames like “breakbone fever.”

The term “dengue” is believed to originate from the Swahili phrase Ka-dinga pepo, meaning “cramp-like seizure” or “disease caused by an evil spirit,” reflecting both the severe muscular pain and cultural interpretations of illness at the time.

The virus itself was first isolated in the mid-20th century after advances in virology and laboratory techniques made it possible to identify and characterize viral pathogens. During the 1940s and 1950s, extensive research in Southeast Asia particularly in the Philippines and Thailand revealed that dengue is caused by four distinct serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. This discovery was critical for understanding immunity, as infection with one serotype confers lifelong protection against that specific type but only short-term immunity to the others. Subsequent infections with a different serotype increase the risk of severe dengue due to a phenomenon known as antibody-dependent enhancement (ADE).

These foundational discoveries laid the groundwork for modern surveillance programs, diagnostic tools, and vaccine development efforts, such as the release of the first dengue vaccine (Dengvaxia) in 2015.

Causes and Transmission

Dengue fever results from infection by specific viruses and spreads primarily through mosquitoes.

Dengue Virus Overview

The dengue virus belongs to the Flaviviridae family and the Flavivirus genus. It exists in four closely related but antigenically distinct serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. Infection with one serotype typically provides lifelong immunity to that specific type but only short-term, partial immunity to the others. This means a person can be infected up to four times, each with a different serotype.

All four serotypes are capable of causing illness ranging from mild dengue fever to more severe conditions such as dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS). The virus is a single-stranded RNA virus with an envelope that helps it attach to and enter host cells, particularly immune system cells such as monocytes and dendritic cells. Once inside, the virus replicates and spreads through the bloodstream, prompting an immune response that leads to symptoms such as fever, rash, and joint pain.

Severe dengue is often associated with secondary infections by a different serotype due to a phenomenon known as antibody-dependent enhancement (ADE). In ADE, non-neutralizing antibodies from a previous dengue infection facilitate the entry of a new serotype into host cells, potentially increasing disease severity.

Mosquito Vectors

The primary mosquito species responsible for transmitting dengue are Aedes aegypti and Aedes albopictus.

Aedes aegypti is considered the most efficient dengue vector because of its strong preference for feeding on humans, its tendency to bite multiple times in a single feeding period, and its high adaptability to urban environments. It is active mainly during early morning and late afternoon hours. These mosquitoes breed in stagnant water, often in artificial containers such as buckets, discarded tires, water storage tanks, and flower pots.
Aedes albopictus, known as the Asian tiger mosquito, is less specialized in human feeding but has a broader habitat range. It can survive in both tropical and temperate climates and is more common in suburban and rural areas. Although it is less efficient at transmitting dengue compared to Aedes aegypti, it has been responsible for outbreaks in regions where Aedes aegypti is absent.

Both species can lay eggs that survive for months in dry conditions, hatching once they come into contact with water.

Transmission Cycle

The dengue virus is sustained in nature primarily through a human–mosquito–human transmission cycle, which is most common in urban and semi-urban environments. Transmission begins when an uninfected female mosquito bites a person who already has the dengue virus present in their bloodstream.

Once inside the mosquito, the virus multiplies and eventually reaches the salivary glands during an extrinsic incubation period lasting about 8–12 days, depending on factors such as temperature and humidity.

After this period, the mosquito becomes capable of transmitting the virus to another person during a subsequent bite. Infected humans can pass the virus to mosquitoes from shortly before symptoms develop until roughly 5–7 days after the onset of illness.

Humans act as the primary reservoir for the virus in most endemic areas; however, in certain regions of Southeast Asia and West Africa, a sylvatic transmission cycle also exists, involving non-human primates and forest-dwelling Aedes mosquitoes.

While mosquito bites are the primary route of transmission, rare cases of dengue spread through blood transfusion, organ transplantation, or needle-stick injuries have been documented. Maternal transmission from an infected mother to her baby during pregnancy or childbirth is also possible, though uncommon. Vertical transmission within mosquito populations (from adult to offspring) occurs at low rates and is not a major driver of outbreaks.

Symptoms of Dengue Fever

Dengue fever manifests in stages, beginning with subtle signs and progressing to more distinct symptoms. The illness varies in severity, with some cases developing life-threatening complications. Monitoring symptom progression is essential for effective care and timely intervention.

Early Symptoms

The first signs of dengue typically appear 4 to 10 days after being bitten by an infected mosquito. This initial phase often begins abruptly with a high fever, which can reach 104°F (40°C). Headache, particularly pain located behind the eyes (retro-orbital pain), is common during this stage.

Other early symptoms include intense muscle and joint aches, nausea, vomiting, loss of appetite, and general fatigue. A mild skin rash may develop within the first 2 to 5 days of illness. Because these symptoms resemble those of influenza and other viral infections, early dengue can be mistaken for the flu, chikungunya, or Zika virus infection.

Classic Dengue Symptoms

Classic dengue develops after the early phase, lasting about a week. The fever persists and is accompanied by severe muscle and joint pain, often described as “breakbone fever.” This pain can significantly limit mobility.

A characteristic rash may appear, initially blotchy and then spreading. Other symptoms include swelling of lymph nodes and pain behind the eyes. Mild bleeding such as nose or gum bleeding and easy bruising can occur due to low platelet counts.

Severe Dengue Signs

Severe dengue—also known as dengue haemorrhagic fever—is a medical emergency that requires immediate care. It is more likely to occur in people experiencing a second infection with a different dengue serotype due to antibody-dependent enhancement (ADE), although it can also affect first-time cases.

Warning signs of severe dengue include intense and persistent abdominal pain, continuous vomiting, rapid or labored breathing, bleeding under the skin (petechiae), and visible blood in vomit or stool. Patients may also show extreme fatigue, irritability, or restlessness.

As the condition worsens, a sudden drop in blood pressure can occur, leading to dengue shock syndrome. Severe dengue results mainly from plasma leakage—the escape of fluid from blood vessels into surrounding tissues—which can cause fluid buildup in the lungs or abdomen, organ damage, and death if not promptly treated.

Diagnosis Methods

The diagnosis of dengue fever relies on identifying specific symptoms and confirming infection through laboratory tests.

Clinical Evaluation

Diagnosis often begins with a detailed medical history and physical examination. Physicians assess hallmark symptoms such as sudden high fever, severe headache, pain behind the eyes (retro-orbital pain), muscle and joint aches, and skin rash. They also check for early warning signs of severe dengue, including persistent vomiting, abdominal pain, and spontaneous bleeding from the gums or nose.

During the examination, healthcare providers may detect a rapid, weak pulse, low blood pressure, and signs of dehydration, which are more common in advanced or severe cases. In dengue shock syndrome, the skin may appear cold and clammy with delayed capillary refill.

A history of recent travel to or residence in dengue-endemic regions, particularly during outbreak seasons, significantly raises the suspicion of dengue. While clinical presentation can help identify probable cases, these symptoms are not unique to dengue, making laboratory confirmation essential.

Laboratory Testing

Laboratory testing confirms the presence of dengue virus or its effects on the body. Common tests include:

NS1 antigen test: Detects a viral protein (nonstructural protein 1) in the blood during the first 5 days of illness, making it useful for early diagnosis before antibodies appear.
IgM and IgG serology: Measures antibodies produced by the immune system. IgM antibodies generally appear within 4–5 days of symptom onset and indicate a recent infection, while IgG antibodies appear later and indicate past exposure or secondary infection.
PCR (Polymerase Chain Reaction): Identifies viral RNA with high accuracy during the acute phase. It is considered the gold standard for confirming dengue infection.
Complete Blood Count (CBC) – Often reveals low white blood cell count (leukopenia) and low platelet count (thrombocytopenia). A rising hematocrit level may indicate plasma leakage, a sign of severe dengue.

Complete blood count often shows leukopenia and thrombocytopenia, which support clinical findings. Serial testing may be necessary to monitor disease progression.

Differential Diagnosis

Dengue fever shares many clinical features with other tropical and viral illnesses, making differential diagnosis essential. Diseases such as malaria, chikungunya, Zika virus infection, leptospirosis, typhoid fever, and influenza can all present with fever, headache, rash, and body aches.

Malaria is ruled out through microscopic examination of blood smears or rapid diagnostic tests.
Chikungunya and Zika can be differentiated using specific antibody tests or PCR.
Leptospirosis may present with jaundice and kidney involvement and is confirmed through serology or culture.
Typhoid fever is diagnosed using blood cultures or the Widal test.

Careful evaluation of symptom onset, travel history, exposure risk, and disease progression is essential to avoid misdiagnosis. In areas where multiple mosquito-borne diseases are present, co-infections can occur, making laboratory confirmation even more important.

Treatment Options

Treatment for dengue fever centers on managing symptoms and preventing complications. It requires careful monitoring and specific interventions depending on disease severity.

Supportive Care

For most patients, dengue management is based on supportive therapy. Bed rest is recommended during the febrile phase to conserve energy and help the body fight the infection. Adequate hydration is a key priority, as fever, vomiting, and plasma leakage can lead to dehydration. Patients are encouraged to drink water, oral rehydration solutions (ORS), soups, or fruit juices. In cases of moderate dehydration, oral rehydration therapy is used, while severe dehydration may require intravenous (IV) fluid replacement.

Pain and fever management is achieved using acetaminophen (paracetamol), as it reduces fever without increasing bleeding risk. NSAIDs such as ibuprofen, aspirin, and naproxen are avoided because they can aggravate bleeding tendencies by affecting platelet function and irritating the stomach lining.

Patients recovering at home are advised to monitor for warning signs, such as worsening abdominal pain, persistent vomiting, dizziness, bleeding gums, nosebleeds, blood in stool or vomit, or unusual fatigue. Daily monitoring of fluid intake and urine output helps detect dehydration early, while checking temperature trends and general well-being can signal complications before they escalate.

Hospitalization Criteria

Hospital admission is indicated when patients develop severe dengue symptoms or show early signs of complications. Warning signs that necessitate hospitalization include:

Severe bleeding from gums, nose, or gastrointestinal tract
Signs of plasma leakage, such as fluid accumulation around the lungs (pleural effusion) or abdomen (ascites)
Severe abdominal pain or persistent vomiting
Sudden drop in blood pressure (hypotension) or rapid, weak pulse
Altered mental status, confusion, or restlessness
Laboratory evidence of rapid platelet decline, rising hematocrit, or elevated liver enzymes
Severe dehydration or organ dysfunction (e.g., liver or kidney impairment)

In hospital settings, close monitoring of vital signs, urine output, platelet counts, and hematocrit levels is carried out. Fluid therapy is carefully managed to avoid both under-hydration, which may worsen shock, and over-hydration, which can lead to pulmonary edema. In cases of severe bleeding, blood transfusions or platelet transfusions may be required.

Severe dengue, which includes dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS), requires intensive care. The priority is to restore and maintain blood volume through rapid IV fluid administration while avoiding complications from excessive fluid therapy.

Oxygen supplementation may be necessary in patients with respiratory distress.
Electrolyte monitoring ensures balance during fluid replacement.
In rare cases, mechanical ventilation or dialysis may be needed if organ failure occurs.

Early and aggressive management during the critical phase (when fever subsides but plasma leakage risk is highest) significantly reduces mortality rates.

Emerging Therapies

Although supportive care remains the cornerstone of treatment, research is ongoing to develop targeted therapies that directly combat the dengue virus or regulate the body’s immune response.

Antiviral drugs – Experimental compounds aim to block viral replication by targeting specific viral proteins, such as the NS5 RNA polymerase or the NS3 protease.
Monoclonal antibodies – Laboratory-engineered antibodies are being studied for their ability to neutralize dengue virus and prevent it from entering host cells.
Host-directed therapies – Immunomodulatory drugs seek to control the overactive immune response that contributes to severe dengue complications.

Some candidates have shown promise in preclinical and early clinical trials, but none have yet become part of routine medical practice.

Prevention and Control

Effective prevention and control of dengue fever rely on reducing mosquito populations, protecting individuals from bites, and advancing vaccine availability. Coordinated efforts at community and individual levels play critical roles in minimizing transmission.

Mosquito Control Strategies

Elimination of breeding sites by regularly emptying, cleaning, or covering containers that collect water, such as buckets, barrels, tires, flowerpots, and roof gutters.
Municipal larviciding programs targeting water storage facilities, drains, and stagnant pools to kill mosquito larvae before they mature into adults.
Adulticiding (fogging) using approved insecticides to rapidly reduce adult mosquito populations during outbreaks or in high-risk areas.
Biological control initiatives such as introducing Wolbachia-infected mosquitoes, which reduce the ability of Aedes mosquitoes to transmit the virus.
Predator-based control by encouraging natural predators like certain fish species (Poecilia reticulata or guppies) in water bodies to consume mosquito larvae.
Environmental sanitation campaigns to ensure proper waste disposal, regular clearing of vegetation around homes, and drainage of stagnant water from streets and vacant lots.
Surveillance systems using ovitraps, adult mosquito traps, and larval surveys to monitor mosquito density and guide timely interventions.
Community mobilization programs that involve residents in identifying breeding sites, reporting problem areas, and participating in cleanup drives.

Personal Protection Measures

Use of mosquito repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus, applied to exposed skin and clothing as per product instructions.
Wearing protective clothing, including long-sleeved shirts, long pants, socks, and light-colored fabrics that make it harder for mosquitoes to spot and bite.
Avoiding outdoor exposure during peak Aedes mosquito activity periods—early morning and late afternoon—whenever possible.
Sleeping under insecticide-treated mosquito nets, especially in areas without screened housing or for vulnerable populations like children, pregnant women, and the elderly.
Installing physical barriers such as fine-mesh window screens, door screens, and air curtains to prevent mosquito entry into living spaces.
Using indoor insecticide sprays or mosquito coils in enclosed spaces to kill or repel mosquitoes.
Regular inspection and emptying of domestic water storage containers, including pet water bowls, plant saucers, and rooftop tanks.
Educating travelers to endemic regions on personal protective measures and the importance of early medical consultation if symptoms appear.

Vaccination Developments

Several dengue vaccines are under development, with a few already licensed in specific countries. The most widely known is CYD-TDV (Dengvaxia), which is approved in select countries for individuals aged 9–45 who have laboratory-confirmed prior dengue infection. This vaccine has been shown to reduce the risk of severe disease and hospitalization but is not recommended for dengue-naïve individuals, as it may increase the risk of severe dengue upon subsequent infection.

New-generation vaccines such as TAK-003, developed by Takeda Pharmaceuticals, have demonstrated promising results in Phase III clinical trials, offering protection across all four dengue virus serotypes, including in seronegative individuals. Another candidate, TV003/TV005, developed by the U.S. National Institutes of Health, is in advanced clinical testing and has shown strong immunogenicity with fewer safety concerns.

Research continues to improve vaccine safety profiles, efficacy, and age-range applicability, aiming to enhance global disease control.

Complications and Risk Factors

Dengue fever can lead to severe health issues that require immediate medical attention. Certain conditions and population groups increase the likelihood of these complications.

Dengue Hemorrhagic Fever

Dengue Hemorrhagic Fever (DHF) is a serious form characterized by bleeding, blood plasma leakage, and low platelet count. Symptoms include severe abdominal pain, persistent vomiting, and bleeding under the skin, gums, or nose.

DHF arises mainly during a second infection with a different dengue virus serotype. It can cause fluid accumulation, respiratory distress, and in severe cases, organ damage. Timely diagnosis and supportive treatment are critical to reduce fatality risks.

Dengue Shock Syndrome

Dengue Shock Syndrome represents the most critical and life-threatening progression of severe dengue. It develops when extensive plasma leakage reduces the circulating blood volume to the point of circulatory collapse. DSS is often preceded by DHF and tends to occur within 24–48 hours after the fever subsides, a period that can mislead patients into believing they are recovering.

The clinical features of DSS include extremely low blood pressure, rapid and weak pulse, cold and clammy skin, and changes in mental status such as confusion, restlessness, or lethargy. If not treated immediately, inadequate tissue perfusion can lead to acute kidney injury, liver failure, or cardiac dysfunction. Treatment requires urgent hospitalization, preferably in an intensive care unit, where patients can receive rapid intravenous crystalloid infusion to restore blood volume. In some cases, colloid solutions may be needed if shock persists despite initial treatment. Continuous monitoring of vital signs, urine output, and laboratory parameters is essential to guide fluid management and prevent complications from overhydration.

At-Risk Populations

Not all individuals face the same risk of developing severe dengue complications. Those with a prior history of dengue infection are particularly vulnerable due to ADE, which increases the severity of subsequent infections. Children, especially those under 15 years of age, are more prone to rapid plasma leakage and may deteriorate quickly without showing early warning signs, making close observation essential. Elderly individuals also face higher risks due to weakened immunity and the likelihood of coexisting medical conditions.

Patients with chronic illnesses such as diabetes, hypertension, cardiovascular disease, obesity, or asthma are at increased risk because their underlying health conditions may amplify the body’s inflammatory response or impair its ability to compensate for fluid shifts. Pregnant women face unique risks, including higher chances of hemorrhage during childbirth and the potential for transmitting the virus to the newborn.

Environmental and social factors also play a role. Individuals living in densely populated urban areas with inadequate sanitation, poor waste management, and high mosquito density are at greater risk of both infection and reinfection. Similarly, travelers to dengue-endemic regions may be at risk if they lack prior immunity. For these populations, preventive measures such as strict mosquito bite protection, community-level vector control, and timely medical evaluation at the onset of symptoms are critical to reducing the risk of severe outcomes.