Below is a detailed explanation of dengue fever, expanded with current information from the World Health Organization (WHO).
🦟 1. What is dengue fever?
Dengue is a viral infection caused by the dengue virus (DENV). It is mainly transmitted by the bite of an infected female Aedes mosquito, particularly Aedes aegypti. These mosquitoes commonly bite during the day, including early morning and late afternoon.
There are four major dengue virus serotypes:
- DENV-1
- DENV-2
- DENV-3
- DENV-4
Being infected with one serotype generally gives long-term protection against that same serotype, but protection against the others is not permanent. A second dengue infection with a different serotype can increase the risk of severe dengue.
🦠 2. How does dengue spread?
The usual cycle is:
Infected person → mosquito bites person → mosquito becomes infected → mosquito bites another person → new infection
A mosquito becomes infected when it bites a person who has dengue virus circulating in their blood. After the virus develops inside the mosquito, that mosquito can transmit dengue when it bites another person.
Dengue is not normally spread directly from one person to another like influenza or COVID-19.
However, an infected person can infect mosquitoes that bite them, so preventing mosquito bites while sick is important.
Rare transmission through blood products, organ transplantation, and from a pregnant mother to her baby has also been reported.
🌡️ 3. Incubation period
After an infected mosquito bites you, symptoms generally appear approximately:
4–10 days later
Some people never develop symptoms, while others develop a flu-like illness.
🤒 4. Symptoms of dengue
Many dengue infections are asymptomatic or mild.
When symptoms occur, common symptoms include:
High fever
Dengue can cause a sudden, high fever, sometimes around 40°C / 104°F.
Severe headache
A strong headache is common.
Pain behind the eyes
Some people experience significant pain, especially when moving their eyes.
Muscle and joint pain
Dengue is sometimes called “break-bone fever” because the body and joint aches can be severe.
Nausea and vomiting
Digestive symptoms are common.
Rash
A red or blotchy rash can develop during the illness.
Other symptoms
- Fatigue
- Weakness
- Swollen glands
- Reduced appetite
These symptoms can resemble influenza and other infections, so symptoms alone cannot reliably confirm dengue.
⏳ 5. The important stages of dengue
Understanding the stages is particularly important because a person can appear to be improving while actually entering the dangerous phase.
Stage 1 — Febrile phase
Usually lasts around 2–7 days.
Typical features include:
- High fever
- Headache
- Muscle/joint pain
- Pain behind the eyes
- Nausea/vomiting
- Rash
During this stage, it may be difficult to determine whether a person will develop severe dengue.
Stage 2 — Critical phase
This is the stage that requires the most attention.
It often occurs around the time the fever starts coming down, commonly around days 3–7 of illness.
Important: A falling temperature does not automatically mean the person is recovering.
Some patients develop leakage of plasma from blood vessels. This can cause:
- Low blood pressure
- Shock
- Fluid accumulation
- Breathing difficulty
- Severe bleeding
- Organ damage
Stage 3 — Recovery phase
If the patient gets through the critical phase without complications, the body begins to recover and the leaked fluid is gradually reabsorbed.
Most people with uncomplicated dengue recover within 1–2 weeks, although tiredness can persist for several weeks.
🚨 6. Warning signs of severe dengue
This is probably the most important part to understand.
Seek urgent medical attention if someone with suspected or confirmed dengue develops:
- Severe abdominal pain
- Persistent vomiting
- Bleeding from the nose or gums
- Vomiting blood
- Blood in the stool
- Rapid breathing
- Extreme weakness or fatigue
- Restlessness
- Extreme thirst
- Pale, cold skin
- Significant weakness
- Signs of shock or breathing difficulty
These warning signs can appear after the fever decreases, which is why the period immediately after the fever breaks can be dangerous.
🚑 Do not wait for the fever to return.
If warning signs appear, the person should be evaluated immediately, often in an emergency department or hospital.
🩸 7. Why can dengue cause bleeding?
Dengue can affect the blood vessels and the body’s clotting system.
In severe dengue, increased permeability of blood vessels can cause plasma leakage. Severe disease can also involve low platelet counts and abnormalities in coagulation.
This can contribute to:
- Nose bleeding
- Gum bleeding
- Skin bleeding
- Gastrointestinal bleeding
- Severe internal bleeding in extreme cases
Severe dengue can also cause organ impairment, particularly involving the liver and other organs.
🧪 8. How is dengue diagnosed?
A doctor may suspect dengue based on:
- Fever
- Symptoms
- Physical examination
- Recent travel or residence in a dengue-risk area
- Local outbreaks
- Blood tests
Laboratory testing can include methods that detect the virus, viral genetic material, or dengue antibodies, depending on how many days the patient has been ill.
A CBC (complete blood count) is also commonly monitored in clinical care, particularly platelet count and hematocrit, because changes can help doctors assess disease progression.
However, a low platelet count alone does not tell you how severe the disease is. The patient’s overall condition and warning signs are extremely important.
💊 9. Is there a medicine that cures dengue?
Currently, there is no specific antiviral treatment that cures dengue infection.
Treatment is mainly supportive:
Rest
Get adequate rest.
Fluids
Maintaining adequate hydration is important.
Doctors may recommend oral fluids or, when necessary, intravenous fluids.
Fever/pain
Acetaminophen (paracetamol) is generally used for fever and pain when appropriate.
⚠️ Avoid aspirin and ibuprofen unless a healthcare professional specifically tells you otherwise.
WHO recommends avoiding aspirin and NSAIDs such as ibuprofen because they can increase the risk of bleeding in dengue.
Do not start or stop medications based solely on a video.
💧 10. Why hydration is so important
Dengue can cause:
fever + vomiting + reduced intake + fluid leakage
which can lead to dehydration and, in severe cases, circulatory problems.
Doctors therefore pay close attention to:
- Blood pressure
- Heart rate
- Urine output
- Hydration status
- Hematocrit
- Other blood-test results
- Warning signs
For severe dengue, careful fluid management in hospital can be lifesaving.
🦟 11. How to prevent dengue
Because dengue is transmitted by mosquitoes, preventing mosquito bites is extremely important.
Protect yourself
Use:
- Mosquito repellent
- Long sleeves
- Long pants
- Window/door screens
- Air conditioning or fans
- Mosquito nets when appropriate
WHO specifically lists repellents containing ingredients such as DEET, picaridin, or IR3535 as options for mosquito protection.
Remove mosquito breeding sites
Aedes mosquitoes can breed in relatively small amounts of standing water.
Regularly:
- Empty containers holding water
- Clean water-storage containers
- Cover water containers
- Remove discarded containers
- Empty standing water around the home
- Clean outdoor areas
WHO recommends covering, emptying and cleaning domestic water-storage containers regularly.
💉 12. What about the dengue vaccine?
There are dengue vaccines, but vaccination recommendations depend heavily on the vaccine, age, previous dengue infection, country, and local transmission level.
For example, WHO’s current recommendations for Qdenga (TAK-003) are targeted to specific populations/settings rather than recommending universal vaccination everywhere.
So if you’re considering dengue vaccination, the appropriate vaccine and eligibility should be discussed with a doctor or travel clinic based on your individual circumstances.
🧠 13. Why is a second dengue infection sometimes more dangerous?
This is an important concept.
Suppose someone previously had:
DENV-1
and later becomes infected with:
DENV-2
The immune response to the first infection does not necessarily provide complete protection against the second serotype.
A subsequent infection with a different serotype is associated with an increased risk of severe dengue.
This doesn’t mean that every second infection becomes severe—most dengue infections remain mild—but the risk is higher.
🩺 14. Dengue vs severe dengue
| Dengue | Severe dengue |
|---|---|
| High fever | Severe abdominal pain |
| Headache | Persistent vomiting |
| Pain behind eyes | Significant bleeding |
| Muscle/joint pain | Shock/low blood pressure |
| Nausea | Breathing difficulty |
| Rash | Organ impairment |
| Fatigue | Potentially life-threatening |
Most people recover, but severe dengue requires prompt medical treatment.
⭐ The most important takeaway
If you remember only five things, remember these:
- Dengue is caused by a virus transmitted primarily by Aedes mosquitoes.
- Symptoms usually begin 4–10 days after infection and can include high fever, headache, eye pain, body/joint aches, nausea and rash.
- The dangerous period can begin when the fever goes down.
- Severe abdominal pain, persistent vomiting, bleeding, rapid breathing, extreme weakness, pale/cold skin or other warning signs require urgent medical care.
- There is no specific cure; treatment focuses on fluids, monitoring and symptom control, and aspirin/ibuprofen should generally be avoided because of bleeding risk.
The video you provided: Watch “Doctor explains Dengue Fever | Causes, Symptoms, Treatment and Prevention”
If you are asking because you or someone you know currently has fever/suspected dengue, tell me the age, day of illness (e.g., day 3), temperature, symptoms, platelet count/CBC if available, and any vomiting/bleeding/abdominal pain, and I can explain what those findings generally mean and which warning signs are most important.