Introduction
Mosquitoes spread dengue viruses and can infect people, sometimes causing illness. The infection can show up in three ways: (a) “classic” dengue fever, (b) dengue hemorrhagic fever (DHF) without shock, or (c) dengue hemorrhagic fever with shock (DSS).
Dengue fever is usually mild and goes away on its own. This is the most common form of the disease. Areas with many Aedes mosquitoes (like Aedes aegypti and Aedes albopictus) and more than one type of dengue virus often experience outbreaks of the more severe forms, like DHF and DSS.
Understanding the Dengue Syndrome: A Growing Global Health Concern
Dengue fever is the most common disease transmitted by arthropods, such as mosquitoes. It’s a rapidly emerging health threat in tropical and subtropical regions, especially in urban and nearby areas. Over the last 30 years, the disease has spread significantly, with a sharp rise in reported cases. Currently, around 2.5 to 3 billion people live in areas where dengue can be transmitted by mosquitoes.
A significant dengue outbreak occurred in 1998 when 1.2 million cases of dengue fever and dengue hemorrhagic fever (DHF) were reported across 56 countries. This pandemic was unprecedented, and by 2001, similar numbers of cases were being reported. However, only a small proportion of cases are officially reported to the World Health Organization (WHO). Each year, it is estimated that dengue infects about 50 million people, with 500,000 cases of DHF and at least 12,000 deaths, mostly among children. The actual death toll could be twice as high.
The rapid increase in dengue and DHF can be attributed to several factors: unchecked population growth, urbanization without proper water management, increased travel and trade, and weakening mosquito control programs. The primary mosquito responsible for spreading dengue is Aedes aegypti, while the role of Aedes albopictus remains uncertain.
Dengue Risk Across Countries
Countries affected by dengue in Southeast Asia and surrounding regions are classified into different categories based on the severity and spread of the disease:
- Category A (Indonesia, Myanmar, Thailand): Dengue is a major public health issue, leading to hospitalizations and deaths, particularly among children. The disease is now spreading to rural areas.
- Category B (India, Bangladesh, Maldives, Sri Lanka): DHF is becoming more common, with outbreaks occurring more frequently. The disease is spreading geographically, with Aedes aegypti being the main mosquito spreading the virus, though the role of Aedes albopictus is still uncertain.
- Category C (Bhutan, Nepal): No reported cases and the presence of the disease remains uncertain.
- Category D (North Korea): Dengue is not present in this region.
Dengue in India and Southeast Asia
Dengue and DHF are widespread in India, where all four types of the dengue virus circulate. Since 1996, 18 states have reported the disease, putting around 450 million people at risk. Other Southeast Asian countries, including Bangladesh, Indonesia, Myanmar, Sri Lanka, and Thailand, have also experienced large outbreaks, and these countries now consider dengue endemic.
Over the past 15 years, all four subtypes of the dengue virus have been detected in India, Indonesia, Myanmar, and Sri Lanka. DEN-2 and DEN-3 have also been found in the Maldives and Bangladesh. Dengue is one of the leading causes of hospitalization and death among children in Southeast Asia, following diarrheal diseases and acute respiratory infections. The number of dengue cases in the region is estimated to be between 20 to 30 million annually, with around 200,000 cases of DHF. However, the actual number of cases reported by countries is much lower, and fatality rates remain high, especially in countries where the disease is most prevalent, with death rates averaging around 3.5%.
What is Classical Dengue Fever?
Classical dengue, also known as “breakbone fever,” is a viral infection that has been present in India for a long time. It is caused by four different types (serotypes) of the dengue virus: 1, 2, 3, and 4. Dengue fever can occur as isolated cases (endemic) or during widespread outbreaks (epidemic), often seen during the rainy season when mosquito populations are high.
Transmission of Dengue Fever
The dengue virus is spread by mosquitoes, primarily Aedes aegypti. Other species like Aedes albopictus can also carry the virus. The transmission cycle is “man-mosquito-man.”
A mosquito becomes infective after biting a person with dengue during the first 5 days of illness. After an incubation period of 8 to 10 days, the mosquito can transmit the virus for the rest of its life.
Who Can Get This Disease?
Dengue fever affects all age groups and genders, although children generally have a milder form of the illness compared to adults. Once a person is infected with one type of the virus, they gain immunity to that specific type but only partial protection against the others.
Symptoms of Classical Dengue Fever
The symptoms of dengue fever typically appear 3 to 10 days after the mosquito bite, with an average incubation period of 5 to 6 days. Symptoms come on suddenly and may include:
- High fever (39°C to 40°C)
- Severe headache
- Intense muscle and joint pain (hence the term “breakbone fever”)
- Pain behind the eyes
- Light sensitivity
- Extreme fatigue and loss of appetite
Rash and Skin Changes
Around 80% of dengue cases develop a rash during the fever’s remission or second phase. The rash typically starts on the chest and spreads to the arms and legs, and it may cause itching. This skin reaction can last anywhere from a few hours to several days, with possible skin peeling afterward.
Duration and Recovery
The fever usually lasts about 5 days, rarely exceeding 7 days. Most people recover completely, but it can take time for some individuals to regain their full energy. Fortunately, the fatality rate is extremely low for classical dengue fever.
What is Dengue Hemorrhagic Fever (DHF)?
Dengue Hemorrhagic Fever (DHF) is a severe and potentially life-threatening form of dengue fever. It occurs when a person is infected by more than one type of dengue virus, which triggers a serious immune reaction. DHF is more dangerous than classical dengue because it can lead to complications like bleeding, organ damage, and shock.
Causes of DHF
DHF is caused by infection with multiple dengue virus serotypes. The first infection with one serotype makes a person more vulnerable to severe illness if they are later infected with another serotype. This leads to an immune system overreaction, often referred to as an “immunological catastrophe.”
Transmission of DHF
Like classical dengue, DHF is transmitted by the Aedes aegypti mosquito. After biting an infected person, the mosquito carries the virus and can transmit it to others after an incubation period of 8 to 10 days. DHF typically spreads in areas where mosquitoes are abundant, especially during the rainy season.
Symptoms of DHF
After an incubation period of 4 to 6 days, DHF begins suddenly with high fever, facial flushing, and severe headache. Common symptoms also include:
- Loss of appetite
- Vomiting
- Abdominal pain, particularly in the upper right part of the abdomen
- Tenderness around the liver area In the early stages, DHF may resemble classical dengue fever, but a rash is less common.
Severe Complications of DHF
The major difference between DHF and classical dengue fever is the potential for severe complications, which are caused by two key factors:
- Plasma Leakage: Fluid leaks from blood vessels into surrounding tissues, leading to low blood pressure and shock.
- Abnormal Blood Clotting: The blood’s ability to clot is reduced, which can result in severe bleeding.
Risk Factors for DHF
While DHF can affect people of all ages, young children and those who have had a previous dengue infection are at higher risk. Early detection and proper medical treatment are crucial for managing DHF and preventing its severe complications.
Criteria for Clinical Diagnosis of DHF
Dengue Hemorrhagic Fever (DHF) is diagnosed based on specific clinical manifestations. These signs indicate DHF without shock and are important for early detection and treatment.
Clinical Diagnosis
- Fever: Sudden onset of high fever that is continuous and lasts for 2 to 7 days.
- Hemorrhagic Manifestations: These include a positive tourniquet test (performed using a blood pressure cuff). A positive result shows more than 20 petechiae (small red or purple spots caused by bleeding) per 2.5 cm (1-inch) square. The test is often positive after recovery from shock. Additionally, the following bleeding signs may be present:
- Petechiae, Purpura, Ecchymosis: Different forms of skin bleeding.
- Epistaxis: Nosebleeds.
- Gum Bleeding.
- Haematemesis and/or Melaena: Vomiting blood or passing black, tarry stools.
- Liver Enlargement: The liver may be enlarged as a sign of DHF.
Grading the Severity of DHF
The severity of DHF is classified into four grades based on the presence of shock and bleeding.
- Grade I: Fever with non-specific constitutional symptoms. The only hemorrhagic manifestation is a positive tourniquet test.
- Grade II: Spontaneous bleeding in the skin or other areas, along with the symptoms of Grade I.
- Grade III: Signs of circulatory failure such as rapid and weak pulse, narrowed pulse pressure (20 mm Hg or less), or hypotension. The patient may also have cold, clammy skin and be restless.
- Grade IV: Severe shock, where both blood pressure and pulse are undetectable.
The presence of thrombocytopenia (low platelet count) along with haemoconcentration (increase in red blood cell concentration) helps distinguish Grade I and Grade II DHF from classical dengue fever and other diseases.
Laboratory Diagnosis
- Thrombocytopenia: Platelet count of 100,000/mm³ or less.
- Haemoconcentration: An increase in hematocrit (the percentage of red blood cells) by 20% or more from the baseline value.
The combination of fever, hemorrhagic symptoms, thrombocytopenia, and haemoconcentration or rising hematocrit levels is enough to make a clinical diagnosis of DHF.
Dengue Shock Syndrome (DSS)
Clinical Diagnosis of DSS
Dengue Shock Syndrome (DSS) is diagnosed based on the following criteria:
- All the Criteria for DHF: These include the sudden onset of fever, hemorrhagic manifestations (such as a positive tourniquet test and bleeding signs), and liver enlargement.
- Signs of Shock: Shock is indicated by:
- A rapid and weak pulse.
- Narrowing of pulse pressure (20 mm Hg or less) or low blood pressure (hypotension).
- The presence of cold, clammy skin.
- Restlessness or agitation.
These symptoms, combined with the signs of DHF, help confirm the diagnosis of DSS.
Treatment of Dengue Fever
The management of dengue fever is mostly symptomatic and supportive. Here’s how the treatment is typically handled:
- Bed Rest: Bed rest is recommended during the acute fever phase.
- Fever Management: Antipyretics (medications that reduce fever) or sponging can be used to keep body temperature below 40°C. It is important to avoid aspirin, especially in areas where DHF is common, because it may cause gastritis, bleeding, and acidosis.
- Oral Fluid and Electrolytes: Patients who experience excessive sweating, vomiting, or diarrhea should be given oral fluid and electrolyte therapy to prevent dehydration.
Management of DHF
The management of DHF during the fever phase is similar to the treatment for dengue fever. However, as DHF progresses, more careful management is required:
- Haematocrit Monitoring: A rise in hematocrit values (indicating plasma loss) means the patient may need parenteral fluid therapy (fluid administered intravenously). For patients in Grade I and II DHF, volume replacement is needed for 12-24 hours.
- Hospitalization: Patients showing signs of bleeding or having persistently high hematocrit values should be admitted to the hospital. The type and volume of fluid given should be similar to what is used for treating moderate dehydration, but the rate must be adjusted based on the patient’s condition.
- Fluid Volume Management: Fluid volume should be measured and adjusted every 2 to 3 hours over a 24-48 hour period of plasma leakage. Frequent checks of hematocrit and vital signs are essential to ensure the patient is receiving the right amount of fluid.
- Avoid Over-Transfusion: Too much fluid can lead to respiratory problems, such as pulmonary congestion or edema. The fluids commonly used include crystalloids such as 5% dextrose in lactated Ringer’s solution, acetated Ringer’s solution, or saline.
Management of Shock (Dengue Shock Syndrome – DSS)
DSS is a medical emergency that requires immediate fluid replacement therapy. Key aspects of managing DSS include:
- Volume Replacement: In DSS, fluid loss must be replaced quickly. A bolus of 10 ml per kg of body weight of isotonic saline or 5% dextrose in normal saline should be given. If the shock continues, additional fluids like colloidal fluids (such as dextran) may be necessary.
- Blood Transfusion: If the shock persists and the hematocrit values drop despite fluid replacement, a blood transfusion is indicated.
- Monitoring and Adjustments: Once the patient begins to improve, the rate of IV fluid replacement should be gradually reduced and adjusted on an hourly basis. Fluids should be discontinued when the hematocrit reading drops to around 40% and the vital signs are stable.
Fluid Management in Children
In small children, after the initial resuscitation phase, 5% dextrose in half-strength normal saline is commonly used. For infants under one year of age, 5% dextrose in one-third normal saline may be used if the sodium levels are normal.
Stopping IV Fluids
Once the hematocrit levels drop and vital signs stabilize, IV fluid therapy can be discontinued. Indicators of recovery include:
- Strong pulse
- Stable blood pressure
- Good urine output
- Return of appetite
After the leakage phase, plasma that has moved outside the blood vessels will be reabsorbed within 1 to 2 days. Continuing fluids beyond this point could cause hypervolemia, heart failure, or pulmonary edema. Therefore, close monitoring is essential during this recovery period.
It’s also important to note that a drop in hematocrit levels during the reabsorption phase should not be mistaken for internal bleeding. At this stage, stable vital signs like a strong pulse and wide pulse pressure are positive indicators.
Conclusion
Managing dengue fever and its severe forms, such as DHF and DSS, requires timely diagnosis and appropriate medical care. While dengue fever itself is typically self-limiting, supportive treatments such as bed rest, fever management, and adequate fluid intake are crucial to aid recovery. DHF and DSS, however, are more dangerous and demand close monitoring, especially in terms of fluid balance and haemoconcentration.
Early detection, hospitalization for severe cases, and proper fluid replacement can greatly reduce the risk of complications like shock and organ damage. With careful management, most patients recover fully, but the importance of monitoring vital signs and adjusting treatment accordingly cannot be overstated. Educating communities about the importance of seeking early treatment and preventing mosquito bites is vital in reducing the burden of dengue-related complications.
Disclaimer
This is for educational purposes only and is not intended to replace professional medical advice. If you suspect that you or someone else may have dengue fever or any related symptoms, it is crucial to consult a qualified healthcare provider immediately. Only a doctor can provide proper diagnosis and treatment based on individual health conditions. Always seek professional medical guidance for concerns about dengue or any other health-related issues.