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

Find a doctor | Make an appointment

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Why the recent resurgence in Dengue Fever?

An article was recently published in the Straits Times on 17th July 2019 titled “Weekly dengue cases hit 3 1/2-year high”. This is the latest in a series of news articles over the past few months reporting about the resurgence of dengue cases in Singapore. Make no mistake, dengue fever is back and it is on the rise.

The numbers so far..

According to figures released by the National Environment Agency (NEA), 666 dengue cases were recorded between 7th to 13th July 2019. This is the highest weekly total since January 2016, and brings the overall total to 7,374 dengue cases this year. This is a staggering five times more than the 1,481 cases recorded by this time last year. Sadly, dengue fever has also claimed five lives so far this year.
Our country has weathered dengue epidemics before in the past. A total of 14,209 and 8,826 dengue cases were recorded in 2005 and 2007 respectively. The highest ever single-year total was 22,318 cases in 2013, with eight fatalities. In contrast, dengue infections fell to a record 16-year low in 2017 with 2,772 cases, while 2018 had 3,285 cases.
Based on the number of cases so far this year, it is undeniably worrying that we could be heading towards another dengue outbreak.

Why the recent resurgence in Dengue Fever?

Experts believe that this is due to a combination of three main factors: The Aedesmosquito population, the strength of the virus, and immunity of the general population.
The Aedesmosquito population has been noted to be increasing over the past months, with the majority of breeding sites found in homes. Herd immunity is also generally low in Singapore and is likely to have further weakened given the low incidence of dengue cases in the past two years.

The link between Climate Change and Dengue Fever

On a larger scale, global warming may play a detrimental role in dengue transmission. A study was recently published in the journal Nature Microbiologyon 10th June 2019, stating that with rising temperatures, mosquitoes are able to thrive in places where they previously were unable to, thereby expanding the range of dengue fever. Also, warmer temperatures reduce the time taken for an Aedes mosquito to mature into a biting adult.
The study predicts that by 2050, parts of the world that may become dengue-suitable include coastal eastern China and Japan, southeastern USA, central Mexico, northern areas of Argentina, inland areas of Australia and southern Africa.
The study also forecasts that 2.25 billion more people will be at risk of dengue in 2080 compared to 2015, bringing the total population at risk to over 6.1 billion, or 60% of the world’s population.

A Recap of Dengue Fever

Dengue fever is a vector-borne disease caused by the dengue virus, and is carried and transmitted by the bite of an infective female Aedesmosquito. When a mosquito bites a person infected with the dengue virus, the virus enters the mosquito. Thereafter, it remains infective for the rest of its lifespan. Dengue fever does not spread from one person to another.
There are four types of dengue virus circulating in the world, including Singapore. This means that individuals can be infected with dengue up to four times. First-time dengue infections can be severe, especially among the elderly and those with pre-existing medical conditions. Repeat dengue infections are usually more severe, with high risk of developing dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), both of which can be fatal.

Signs and Symptoms

Up to 75% of dengue infections are asymptomatic. If symptoms do occur, they develop after an incubation period ranging from 3 to 14 days, and include the following:

  • Sudden onset high fever for 2 to 7 days
  • Severe headache with retro-orbital (behind the eye) pain
  • Joint and muscle pain
  • Nausea and/or vomiting
  • Skin rash
  • Mild bleeding of the nose and gums or easy bruising of the skin

Most people recover within about 1 week or so, but less than <5% of all cases, the symptoms can worsen and progress into DHF and/or DSS, which is a life-threatening emergency. They include the following:

  • Severe abdominal pain
  • Persistent vomiting with or without blood
  • Bleeding under the skin
  • Bleeding from the nose, mouth and gums
  • Black stools or blood in the stools
  • Clammy, cold skin
  • Restlessness or irritability
  • Fatigue


Your doctor will take a detailed history, in particular, any recent travel history, as well as any contact you may have had with mosquitoes. Dengue fever is diagnosed via blood tests for dengue profile and full blood count.


There is no specific treatment for dengue fever. Instead, treatment for dengue is mainly supportive and depends on the symptoms present. It is recommended to drink plenty of fluids in order to avoid the risk of dehydration. Those who are able to stay well hydrated, are passing urine, and otherwise feeling well, can be managed at home with daily follow-up. Paracetamol can be taken to alleviate pain and reduce fever, but non-steroidal anti-inflammatory drugs (NSAIDs) such as Naproxen and Ibuprofen should be avoided as they can increase the risk of bleeding complications.
Patients who have pre-existing health conditions, “warning signs” of severe dengue fever, or cannot manage daily outpatient follow-up, should be cared for in hospital. Intravenous fluid and electrolyte replacement, platelet and/or blood transfusions may be required.


The key to reducing dengue fever transmission is by controlling the mosquito population and human exposure. On a national level, Singapore has teamed up with other countries to observe ASEAN Dengue Day, which is part of a concerted effort committed to reducing the burden of dengue fever in the region.
The NEA, various agencies and Town Councils are part of an Inter-Agency Dengue Task Force (IADTF), which works to remove potential mosquito breeding habitats containing clean, stagnant water sources in public areas and housing estates.
All members of the public are also strongly encouraged to do their part in preventing and removing such breeding habitats. The NEA advocates people to perform the Five-step Mozzie Wipeout, which is as follows:

  1. Turn the pail
  2. Tip the vase
  3. Flip the flowerpot plate
  4. Loosen the hardened soil
  5. Clear the roof gutter and place Bti insecticide inside

Some precautions that you can take to prevent getting bitten by mosquitoes are:

  • Stay in air-conditioned environment, and install structural barriers such as window screens or insecticide-treated netting
  • When in an area with mosquitoes, expose as little skin as possible by wearing a long-sleeved shirt, long pants, socks and shoes
  • Use mosquito repellent containing at least 10% concentration of diethyltoluamide (DEET), a substance that deters and repels biting insects

The above advice applies also to persons who have been infected with dengue fever.

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

Find a doctor | Make an appointment

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