Meaning and Disease Mechanism
Dengue haemorrhagic fever is a severe form of dengue infection characterised by increased permeability of blood vessels, plasma leakage, low platelet count and bleeding tendency.
The term was used widely in the older classification of dengue. Current clinical classification generally divides dengue into:
- dengue without warning signs;
- dengue with warning signs;
- severe dengue.
Dengue haemorrhagic fever broadly falls within the category of severe dengue, particularly when significant plasma leakage and bleeding are present.
The condition is caused by any of the four dengue virus serotypes:
- DENV-1
- DENV-2
- DENV-3
- DENV-4
After infection, the immune response may become excessively activated. This can damage the inner lining of blood vessels and make capillaries more permeable. As a result, the liquid component of blood leaks into surrounding tissues.
This may lead to:
- reduced circulating blood volume;
- thickening of the blood;
- fluid accumulation around the lungs or abdomen;
- fall in blood pressure;
- shock and organ dysfunction.
A second dengue infection with a different serotype may increase the risk of severe disease in some individuals through antibody-dependent enhancement. Pre-existing antibodies may bind to the new virus without neutralising it effectively, allowing increased viral entry into immune cells.
Clinical Progression and Symptoms
The illness usually begins like ordinary dengue, with:
- sudden high fever;
- headache;
- pain behind the eyes;
- severe muscle and joint pain;
- nausea and vomiting;
- skin rash;
- weakness.
The most dangerous period often begins when the fever starts falling. This stage is known as the critical phase and commonly occurs between the third and seventh day of illness.
A falling fever does not always mean that the patient is recovering. During this period, plasma leakage may increase rapidly.
Important warning signs include:
- severe abdominal pain;
- persistent vomiting;
- bleeding from the nose or gums;
- vomiting of blood;
- black or bloody stool;
- unusual drowsiness or restlessness;
- cold and clammy skin;
- difficulty in breathing;
- reduced urine output;
- sudden weakness or fainting.
Bleeding may appear as small red spots under the skin, easy bruising, gum bleeding or gastrointestinal bleeding. Severe cases may involve heavy bleeding and failure of organs such as the liver, heart or brain.
Diagnosis
Diagnosis is based on clinical symptoms, physical examination and laboratory findings.
Important laboratory changes may include:
- falling platelet count;
- rising haematocrit due to plasma leakage;
- low white blood cell count;
- abnormal liver enzymes;
- evidence of bleeding or clotting disturbance.
An increase in haematocrit together with a rapid fall in platelets is an important indicator of plasma leakage.
Tests used to confirm dengue infection include:
- NS1 antigen test during the early phase;
- RT-PCR for detection of viral genetic material;
- IgM antibody test during the later phase of illness.
Ultrasound or chest imaging may detect fluid accumulation in the abdomen or around the lungs.
Low platelet count alone does not confirm dengue haemorrhagic fever. The diagnosis depends on the overall clinical condition, evidence of plasma leakage, bleeding and circulatory instability.
Treatment and Clinical Management
There is no specific antiviral medicine that routinely cures dengue haemorrhagic fever. Treatment is mainly supportive and focuses on maintaining circulation and preventing shock.
Management may include:
- careful oral or intravenous fluid replacement;
- frequent monitoring of blood pressure and pulse;
- monitoring of urine output;
- repeated haematocrit and platelet assessment;
- oxygen support when required;
- treatment of severe bleeding;
- intensive care in critical cases.
Fluid administration must be carefully controlled. Too little fluid may worsen shock, while excessive fluid may cause pulmonary oedema or respiratory distress, especially during the recovery phase when leaked fluid returns to the bloodstream.
Platelet transfusion is not automatically required merely because the platelet count is low. It is generally considered when there is significant bleeding or when clinically indicated. Unnecessary transfusion can create additional risks.
Paracetamol may be used for fever and pain. Aspirin, ibuprofen and other non-steroidal anti-inflammatory medicines should generally be avoided because they can increase the risk of bleeding.
Early recognition and proper fluid management substantially reduce the risk of death.
Prevention and Public-Health Importance
Prevention depends on controlling Aedes mosquitoes and reducing human exposure to mosquito bites.
Important measures include:
- removing stagnant water from containers;
- covering water-storage tanks;
- cleaning coolers and flowerpots regularly;
- disposing of tyres, cans and bottles;
- using mosquito repellents;
- wearing protective clothing;
- installing window and door screens;
- strengthening disease surveillance.
People suffering from dengue should also be protected from mosquito bites during the early stage of illness. This prevents mosquitoes from acquiring the virus and transmitting it to others.
Vaccines may reduce dengue burden in selected age groups and high-transmission areas, but they do not replace vector control, early diagnosis or clinical monitoring.
The risk of severe dengue is influenced by:
- previous dengue infection;
- viral serotype and strain;
- age and immune status;
- delayed medical attention;
- underlying health conditions.
Conclusion
Dengue haemorrhagic fever is a severe manifestation of dengue in which plasma leakage, bleeding and circulatory failure may develop rapidly. The critical phase often begins when the fever declines, making continuous monitoring essential. Early identification of warning signs and scientifically managed fluid therapy are the most important measures for preventing shock and death.
