Dengue

What is dengue?

Dengue (also called dengue fever) is a viral infection spread to people through the bite of infected mosquitoes. It is one of the most common mosquito-borne illnesses in the world and occurs mainly in tropical and subtropical regions, including parts of Asia, the Pacific, Africa, the Caribbean, and Central and South America. People living in or traveling to these areas can become infected.

The illness is caused by the dengue virus, which exists in four closely related types (called serotypes). Infection with one type gives long-term protection against that same type but only short-term protection against the others. This is why a person can get dengue more than once, and why a second infection with a different type can sometimes be more serious than the first.

Most people who catch the virus have either no symptoms or a mild flu-like illness that gets better on its own within about a week. A smaller number of people develop severe dengue, a potentially life-threatening form that involves leaking of fluid from blood vessels, bleeding, or organ problems. Because it is difficult to predict at the start who will become seriously ill, doctors watch people with dengue closely for warning signs, especially around the time the fever begins to settle.

Dengue affects people of all ages, including children. In hospitals it is usually managed by infectious disease specialists, general physicians, and pediatricians. At Acibadem, the Infectious Diseases Department is the unit that evaluates and manages this condition.

Dengue symptoms

Dengue symptoms usually begin four to ten days after a bite from an infected mosquito. Many infections are so mild that they are mistaken for another viral illness. When symptoms do appear, they often come on suddenly and may include:

• High fever, often reaching 40°C (104°F)
• Severe headache
• Pain behind the eyes
• Muscle, bone, and joint pain (dengue is sometimes nicknamed “breakbone fever” because of this)
• Nausea and vomiting
• Swollen glands
• A skin rash, which may appear a few days after the fever starts
• Loss of appetite and extreme tiredness

Doctors often describe dengue in three phases. Understanding these can help patients and families know what to expect.

Febrile phase. This is the period of high fever, usually lasting two to seven days. Headache, body aches, and rash are most common during this stage. Mild bleeding from the nose or gums, or small red or purple spots on the skin (called petechiae), can occur.

Critical phase. As the fever comes down, usually between days three and seven of illness, a small proportion of people enter a critical phase. During this window, fluid can leak out of the blood vessels into the surrounding tissues and body cavities. This is when warning signs of severe dengue are most likely to appear. The critical phase generally lasts one to two days. It is important to know that feeling the fever break does not always mean the illness is over.

Recovery phase. Leaked fluid is gradually reabsorbed, appetite returns, and energy slowly improves. Some people develop a second rash, often itchy, during recovery. Fatigue and low mood can linger for days or weeks after other symptoms resolve.

Severe dengue (previously called dengue hemorrhagic fever or dengue shock syndrome) is marked by serious plasma leakage, significant bleeding, or damage to organs such as the liver or heart. Its warning signs are described in the final section of this page and should always be treated as urgent.

Dengue causes and risk factors

The direct cause of dengue is infection with the dengue virus. The virus is passed to humans almost entirely through mosquito bites, primarily from the Aedes aegypti mosquito and, to a lesser extent, the Aedes albopictus mosquito. These mosquitoes bite mainly during the daytime, with peaks in the early morning and late afternoon, and they breed in small pools of standing water such as flowerpots, buckets, discarded tires, and water storage containers.

The cycle works like this: a mosquito bites a person who already has the virus in their blood, the virus multiplies inside the mosquito, and the mosquito then passes it on when it bites someone else. Dengue does not spread directly from person to person through casual contact, coughing, or sneezing. Rare transmission through blood transfusion, organ transplant, or from a pregnant woman to her baby has been reported.

Factors that increase the risk of catching dengue or of developing a more serious illness include:

• Living in or traveling to areas where dengue is common, especially urban and semi-urban areas in tropical climates
• Rainy or warm seasons, when mosquito populations increase
• Previous dengue infection, because a second infection with a different virus type is associated with a higher chance of severe dengue
• Infancy and young childhood, as well as older age
• Pregnancy, which may increase the risk of complications for both mother and baby
• Long-term health conditions such as diabetes, kidney disease, heart disease, or asthma
• Poor access to mosquito control, such as living without window screens or near uncovered water storage

Dengue diagnosis

Dengue can be difficult to diagnose from symptoms alone because its early features overlap with other infections such as influenza, malaria, chikungunya, Zika, typhoid, and leptospirosis. Doctors usually begin by asking about recent travel, where you live, the timing of the fever, and any bleeding or warning signs. They will examine you for rash, tenderness in the abdomen, signs of dehydration, and evidence of bleeding.

Laboratory tests are used to confirm dengue and to monitor its severity. Common tests include:

• NS1 antigen test. This detects a protein produced by the virus and is most useful in the first several days of illness, when the virus is still circulating in the blood.
• PCR (polymerase chain reaction) test. This detects the genetic material of the virus itself and can identify which serotype is involved. It is also most reliable early in the illness.
• Antibody tests (IgM and IgG serology). These look for the immune system’s response to the virus. IgM antibodies usually appear toward the end of the first week, so this test may be negative if done too early. A second sample taken later is sometimes needed to confirm the result.
• Complete blood count. This measures platelets (cells that help blood clot), white blood cells, and hematocrit (the proportion of blood made up of red cells). A falling platelet count together with a rising hematocrit can be an early indicator of plasma leakage and is often checked daily during the critical phase.
• Liver function tests and other blood chemistry. These help assess whether the liver, kidneys, or other organs are affected.

Imaging is not needed to diagnose dengue, but an ultrasound of the chest or abdomen may be used in some cases to look for fluid collections around the lungs, in the abdomen, or thickening of the gallbladder wall, which can support a diagnosis of plasma leakage. A chest X-ray may occasionally be ordered for the same purpose.

Doctors also classify dengue using internationally recognized criteria that separate cases into dengue without warning signs, dengue with warning signs, and severe dengue. This classification, rather than any single test result, guides decisions about whether a person can be cared for at home or should be admitted to the hospital.

Dengue treatment options

There is currently no specific antiviral medicine that cures dengue. Treatment is supportive, meaning it aims to keep the body stable, relieve symptoms, and prevent or manage complications while the immune system clears the virus. The approach depends on how sick the person is and whether warning signs are present.

Care at home for mild dengue. Many people with dengue and no warning signs can recover at home with medical guidance. The main elements are:

• Rest. Fatigue is common and the body needs time to recover.
• Fluids. Drinking plenty of water, oral rehydration solutions, soups, or diluted juices helps prevent dehydration caused by fever, vomiting, and poor appetite.
• Fever and pain relief with acetaminophen (paracetamol). This is generally the preferred medicine. Your doctor will advise on the correct dose and how often to take it.
• Avoiding certain painkillers. Aspirin, ibuprofen, naproxen, and other nonsteroidal anti-inflammatory drugs (NSAIDs) are usually avoided because they can increase the risk of bleeding and may irritate the stomach.
• Daily monitoring. Doctors often ask people recovering at home to return for repeat blood tests, especially around the time the fever settles, and to watch carefully for warning signs.

Hospital care for dengue with warning signs. If warning signs appear, or if a person belongs to a higher-risk group (such as infants, pregnant women, older adults, or people with chronic illness), doctors may recommend admission to the hospital. Care in the hospital typically involves close monitoring of vital signs, urine output, and blood tests, along with intravenous (IV) fluids given carefully through a vein to replace what is leaking from the blood vessels. The amount of fluid is adjusted frequently, since both too little and too much can cause problems.

Intensive care for severe dengue. People with severe dengue, particularly those in shock, need urgent treatment in a high-dependency or intensive care setting. This may include rapid IV fluid resuscitation, oxygen, and in some cases transfusion of blood products if there is significant bleeding. Organ support may be needed if the liver, kidneys, or heart are affected. Platelet transfusions are not given routinely just because the platelet count is low; they are generally reserved for people with active, serious bleeding.

Medicines that are not used. Antibiotics do not work against viruses and are not part of dengue treatment unless a separate bacterial infection is suspected. Corticosteroids have not been shown to be helpful in routine dengue care.

Recovery. There is no formal rehabilitation program for dengue, but recovery can take time. Gradual return to normal activity, good nutrition, and adequate rest are usually advised. Follow-up blood tests may be arranged to confirm that platelet counts and liver tests are returning to normal.

Living with dengue and outlook

For most people, dengue is a short, unpleasant illness that resolves within one to two weeks without lasting problems. The outlook for severe dengue depends heavily on how quickly warning signs are recognized and how promptly supportive care is started. With early detection and appropriate hospital care, many people with severe dengue recover fully, although the condition can be fatal in some cases, particularly when treatment is delayed.

After recovery, some people experience weeks of tiredness, weakness, low mood, or difficulty concentrating. This post-dengue fatigue usually improves gradually on its own. Hair thinning a few months after the illness has also been described and is generally temporary.

Having had dengue once gives lasting immunity to that one virus type but not to the other three. Because a later infection with a different type carries a higher risk of severe illness, people who have recovered from dengue are encouraged to continue protecting themselves from mosquito bites, particularly when living in or visiting areas where the virus circulates.

Dengue vaccines have been developed and are approved in some countries for specific age groups or for people with a documented previous infection. Whether a vaccine is suitable depends on individual circumstances and local recommendations, so this is a question to discuss with a doctor or travel health service.

Preventing mosquito bites remains the most reliable way to reduce risk. Practical measures include wearing long sleeves and trousers, using insect repellent that is approved for use on skin, sleeping under a bed net or in screened or air-conditioned rooms, and removing or covering standing water around the home where mosquitoes breed. People who are ill with dengue should also avoid mosquito bites so that they do not pass the virus on to mosquitoes that could infect others.

Frequently asked questions

What is dengue and how is it spread?

Dengue is an infection caused by the dengue virus, which is carried by Aedes mosquitoes. A person becomes infected when bitten by a mosquito that previously fed on someone carrying the virus. It does not spread through everyday contact between people, so being in the same room as someone with dengue is not a risk in itself.

How long do dengue symptoms last?

Fever and body aches typically last between two and seven days. The complete illness, including the recovery phase, usually lasts one to two weeks, although tiredness can persist for longer. The most important period is the day or two after the fever settles, when warning signs of severe dengue are most likely to appear.

Can dengue be diagnosed with a single blood test?

Often, but not always. Tests that detect the virus directly (NS1 antigen or PCR) work best in the first few days, while antibody tests become positive later. Depending on when you are tested, your doctor may need to repeat a test or combine several results to reach a confident dengue diagnosis.

Is there a cure or specific medicine for dengue?

No specific antiviral treatment for dengue is currently available. Dengue treatment options focus on rest, fluids, fever control with acetaminophen, and careful monitoring. People with warning signs or severe disease are treated in the hospital with intravenous fluids and other supportive care as needed.

Why should I avoid ibuprofen or aspirin if I might have dengue?

Dengue can lower the platelet count and affect blood clotting. Aspirin and NSAIDs such as ibuprofen can further increase bleeding risk and may irritate the stomach lining. For this reason, acetaminophen (paracetamol) is generally recommended for fever and pain, taken according to your doctor’s advice.

Can I get dengue more than once?

Yes. There are four types of dengue virus, and immunity after infection is long-lasting only for the type you had. Infection with a different type later in life is possible and is associated with a higher chance of severe dengue, which is one reason ongoing mosquito bite prevention matters.

What causes some people to develop severe dengue?

The exact reasons are not fully understood. A previous dengue infection with a different virus type is a recognized risk factor. Very young children, older adults, pregnant women, and people with chronic conditions such as diabetes or kidney disease also appear to be at higher risk. Severe dengue can, however, occur in otherwise healthy people, so everyone with dengue should be alert to warning signs.

When to see a doctor

Anyone who develops a high fever after living in or traveling to an area where dengue occurs should see a doctor to be assessed, ideally within the first days of illness. Early evaluation allows blood tests to be arranged and a monitoring plan to be made.

Seek emergency medical care immediately if you or someone you are caring for shows any of the following warning signs, particularly in the first one to two days after the fever comes down:

• Severe or persistent abdominal pain or tenderness
• Persistent vomiting, for example three or more times in a day, or being unable to keep fluids down
• Bleeding from the nose or gums, blood in vomit or stool, black tarry stools, or unusually heavy menstrual bleeding
• Small red or purple spots or large bruises appearing on the skin without injury
• Rapid or difficult breathing
• Extreme tiredness, restlessness, confusion, or irritability
• Cold, clammy, or pale skin, a weak or rapid pulse, or fainting
• Passing very little urine or no urine for several hours
• Fluid build-up, such as a swollen abdomen or new shortness of breath

Infants, pregnant women, older adults, and people with long-term health conditions should be seen promptly even if symptoms seem mild, because their risk of complications is higher. If you are unsure whether a symptom is serious, it is safer to have it checked by a medical professional than to wait.