Dengue Fever Symptoms? Dengue Fever What You Need to Know

Dengue Fever symptoms are divided into 3 phrases – the Febrile Phase, the Critical Phase and the Recovery (or convalescent) Phase.


What is Dengue Fever?

Dengue fever is a mosquito-borne viral infection and is endemic in Singapore. It is carried by the mosquito, Aedes aegypti and its related species, which are abundant in tropical countries. The dengue virus (DEN) comprises 4 serotypes (DEN-1, DEN-2, DEN-3 and DEN-4) which belong to the genus Flavivirus.

The viruses are passed on through the bites of an infective female Aedes mosquito, which mainly acquires the virus while feeding on the blood of an infected person.

Also Read: Why the recent resurgence in Dengue Fever in Singapore?



What are the Symptoms of Dengue Fever?

The incubation period, which is the time between acquiring the infection and appearance of symptoms ranges from 3 to 14 days and symptoms typically develop between 4 and 7 days after the bite on an infected mosquito.


There are 3 Phases of Dengue Fever:

Febrile Phase

Dengue Fever symptoms – This phase is characterized by a sudden high-grade fever (usually 38.5 degrees C or more) and is accompanied by headache, nausea, vomiting, poor appetite, tiredness, muscle aches, joint pains, rash and pain behind the eyes, called retro-orbital pain.

Bleeding manifestations may occur during this phase.


Critical Phase

Dengue Fever symptoms – At the time the fever resolves, the infection enters the critical phase. It is known as the critical phase because potentially, a small proportion of individuals develop complications such as fluid leakage within organs such as around the lungs, abdomen and also bleeding.

The disease may progress to shock and dysfunction of the organs. This phase may last from 24 to 48 hours. Patients may also develop other warning signs during this stage (please see below on “When is dengue fever considered to be severe?”).

It is important to maintain good hydration during this phase (please see below for general advice).


Recovery (or convalescent) Phase

Dengue Fever symptoms – This is the phase during which fluid leakage and bleeding resolve, and vital signs (e.g. blood pressure) and blood tests improve. This can last 2 to 4 days. However, some individuals may still feel fatigued up to weeks after recovery before returning to normal.



What Blood Tests are Usually Performed in Suspected and Established Dengue Fever?

In suspected cases, a dengue antigen (NS1) and serology tests (IgM and IgG) are done to confirm the diagnosis. The NS1 antigen is usually positive during the first few days to a week of illness where as the IgM and IgG tests are typically positive on the fourth day and at 10 to 14 days of illness respectively.

After dengue fever is confirmed, a full blood count is drawn to assess the white blood cells, platelets as well as the haematocrit (measure of the percentage of red blood cells) levels. The platelets are cells in the body that help to form blood clots when bleeding occurs.

A simple example is when an individual sustains a cut on the arm, a complex process involving platelets help to form a clot and heal the cut. If the platelet count in the body is low, there is a tendency for bleeding and slower healing of cuts.

Liver function tests may also be performed as occasionally, the virus can cause inflammation of the liver, called hepatitis which can manifest as abdominal pain and tenderness.

In dengue fever, the white blood cell and platelet counts tend to drop where as the hematocrit may rise which reflects thickened or concentrated blood, a result of fluid leakage and shifts which can occur during the critical phase of dengue fever.

Dengue Fever Test & Dengue Vaccine (Dengvaxia) is available in all our clinics.



What is the Recommended Follow-up of the Individual with Dengue Fever?

The individual is usually advised to return for daily to once in two day follow-ups for repeat full blood count tests to assess the trend of platelet and haematocrit levels.


When is Dengue Fever Considered to be Severe?

Based on the WHO 2009 classification, there is a syndrome called dengue with warning signs and these include:

  • Abdominal pain or tenderness
  • Persistent vomiting
  • Fluid leakage (around the abdomen causing distension and around the lungs causing breathing difficulty)
  • Bleeding
  • Lethargy or restlessness
  • Enlarged liver
  • Increase in haematocrit concurrent with a rapid decrease in platelet count

There is also a syndrome called severe dengue which is dengue fever with at least one of the following:

  • Severe fluid leakage leading to shock and fluid accumulation with respiratory distress
  • Severe bleeding
  • Severe organ involvement (liver, impaired consciousness or any other organ failure)

If any warning signs or signs of severe dengue are present, the clinicians will advice the individual to attend the hospital emergency department as soon as possible.


What Can an Individual Do When He or She Has Confirmed Dengue Fever?

There is no cure for dengue fever. Treatment is usually supportive with careful hydration and monitoring of symptoms and signs of complications. A good indicator of adequate hydration is the colour of urine. If the urine is pale yellow, then hydration is adequate; where as if it is dark yellow and concentrated appearing, then more hydration is needed. Once the dengue fever is in the recovery phase, there is no need for increased hydration.

Most individuals do not develop complications. However, there are those who are at higher risk of developing dengue fever with complications. These are typically elderly individuals or those who have had dengue fever in the past and get infected with a different dengue virus serotype.

Regardless, complications can still occur in any individual and it is imperative that an early review by a clinician is performed to avoid further deterioration at home.



Can Dengue Fever Be Prevented?

Yes. Avoidance of mosquitoes that carry the virus is the best way to prevent dengue fever. This can be done by staying indoors during the day, when mosquitoes that carry the virus are most active, putting up screens and using air conditioners, wearing covered shoes, long-sleeved shirts and long pants and a hat to go outside and using mosquito repellant containing DEET (but do not use DEET on babies younger than 2 months of age). Clothes that are sprayed with a chemical called permethrin can also help.

Lastly, it is important to drain any standing water at home such as wading pools, buckets and potted plants with saucers as mosquitoes breed in standing water. Standing water even the size of a 20 cent coin can encourage mosquito breeding.


Everyone plays a part in dengue fever prevention in the community. Remember that Dengue Fever is deadly. If you suspect that you have the symptoms dengue fever, please visit your doctor for proper danger fever testing. Dengue Vaccine is available in all our clinics.


Speak to your doctor for more information or if you have any questions regarding Dengue Rapid Testing or other Dengue related topics: Dengue in the era of COVID, Dengue Fever Symptoms? Dengue Fever What You Need to Know, Why the recent resurgence in Dengue Fever?, ZIKA IS AN STD!! – Battling the STD Stigma

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