Dengue Fever
- Diagnosis | Management | Prevention -

Dr Urvashi Chongtham *

Dengue outbreak - Fogging in progress on October 14 2023 :: Pix - Waari Singbul Network

Dengue fever is an acute mosquito-borne viral illness common in tropical and subtropical regions, especially in urban and semi- urban areas.

It is caused by the Dengue virus, which has four serotypes, and is transmitted mainly by infected female Aedes aegypti mosquitoes; other Aedes species may also spread it, but usually play a smaller role. Because these mosquitoes commonly bite during the daytime, prevention requires protection throughout the day, not only at night.

The incubation period is usually 4–10 days after infection, and illness commonly lasts 2–7 days. Many infected people have no symptoms, but symptomatic Dengue usually begins with a sudden high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen glands, and a rash.

Most patients recover within 1 to 2 weeks, but a small proportion develop severe Dengue, especially those infected for the second time.

Diagnosis

Diagnosis is based on clinical suspicion, travel or residence in a Dengue-risk area, examination, complete blood count, and specific laboratory tests. In the first week of illness, nucleic acid amplification tests such as RT-PCR, NS1 antigen tests, and IgM antibody tests are useful; Dengue RNA is usually detectable during the first week, and NS1 antigen in serum during 1-5 days indicates current or recent infection.

After 5 days, IgM antibody testing becomes the primary test, though cross-reactivity with other flaviviruses, such as Zika or West Nile, can occur.

Blood counts are crucial in Dengue. A complete blood count helps monitor white blood cell counts, hematocrit, and platelet counts. Leukopenia is common. Rising hematocrit may suggest plasma leakage, which can lead to shock. Platelets are especially important because Dengue of- ten causes thrombocytopenia, or low platelet count.

A fall in platelets alone does not always indicate severe disease, but a rapidly falling count, especially with bleeding signs, rising hematocrit, abdominal pain, vomiting, lethargy, or cold extremities, requires urgent medical review.

Platelet fluctuations are common during the critical phase, often around the time fever settles. A fall may reflect marrow suppression, immune destruction, and increased consumption. However, treatment decisions should be based on the whole clinical picture, not the platelet count alone.

Platelet counts in Dengue fever typically drop rapidly over a 24-to 48-hour window during the critical phase (days 4 to 6 of the illness), before rebounding sharply during recovery.

Timeline of Platelet Fluctuation

Days 1–3 (Febrile Phase) : Counts stay normal or show a mild, gradual decrease.

Days 4–6 (Critical Phase): Counts can plummet drastically over 24 to 48 hours to their lowest point, known as the nadir.

Days 7–10 (Recovery Phase): Counts rise sharply once the fever subsides and typically return to the normal range of 150,000–450,000/µL within a week.

Key Dynamics

Speed of Drop: A drastic fall over 24–48 hours is common, but a low count alone does not automatically mean a transfusion is needed.

Transfusion Effects: Artificially transfused platelets do not remain elevated for long and can drop quickly again if the underlying viral destruction is active.

Daily Tracking: Doctors look at the overall trend through daily complete blood counts (CBC) rather than single readings because numbers can fluctuate dynamically during the critical window

Management

There is no specific antiviral treatment for Dengue. Management is mainly supportive: rest, adequate oral fluids, fever control, and careful monitoring.

Paracetamol or acetaminophen may be used for pain and fever, while aspirin, ibuprofen, and other non-steroidal anti-inflammatory drugs should be avoided because they increase the risk of bleeding. Severe Dengue may require hospitalisation, intravenous fluids, monitoring for shock, and management of bleeding or organ involvement.

Complications and Mortality

Previous infection with Dengue (another serotypes) increases the risk of an individual developing severe dengue. Complications include severe plasma leakage, shock, internal bleeding, severe abdominal pain, persistent vomiting, respiratory distress, liver injury, encephalopathy, and multi-organ failure.

Warning signs often appear after the fever subsides and include severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums or nose, blood in vomit or stool, fatigue, restlessness, thirst, pale, cold skin, and weakness.

Dengue in pregnancy may be associated with preterm birth, low birth weight, and foetal distress. Early recognition and proper care typically result in low mortality rates, though severe dengue can still be fatal. Dengue continues to pose a significant public health challenge worldwide; in 2024, there were over 14.6 million cases and more than 12,000 deaths related to dengue.

Prevention

Prophylaxis depends mainly on mosquito control and bite prevention. People should remove stagnant water, cover and clean water containers weekly, dispose of waste properly, use window screens, wear protective clothing, sleep under nets when needed, and use repellents containing DEET, picaridin, or IR3535.

Public advisories should emphasise early testing, hydration, avoiding self-medication with painkillers that increase bleeding risk, daily monitoring during a fever, and seeking urgent hospital care if warning signs appear.