Severe dengue is a serious and potentially life-threatening progression of dengue fever, a mosquito-borne viral infection. While many dengue infections are mild, a small percentage of individuals develop this more severe form. It is characterized by significant fluid leakage from blood vessels, severe bleeding, or impairment of organs such as the liver or heart.
How Dengue Progresses to Severe Dengue
Dengue infection unfolds in three phases: febrile, critical, and recovery. The febrile phase usually lasts 2-7 days, marked by a high fever, muscle aches, and headache. In some cases, the disease can worsen.
Progression to severe dengue occurs during the “critical phase,” which begins as the fever subsides, typically between days 3 and 7 of the illness, and lasts for 24-48 hours. During this phase, plasma leakage from blood vessels into surrounding tissues, such as the pleural and abdominal cavities, is a heightened risk. This leakage can lead to a drop in blood pressure and hypovolemic shock.
Physiological changes include increased vascular permeability, where the endothelial glycocalyx layer breaks down. This allows plasma proteins like albumin to leak out, contributing to fluid accumulation and thickening of the blood. The immune response plays a role in this increased permeability. A secondary infection with a different dengue serotype after a previous infection significantly increases the risk of developing severe dengue.
Identifying Severe Dengue Symptoms
Identifying the warning signs of severe dengue is important for timely medical intervention. One prominent sign is severe abdominal pain or tenderness, which can be accompanied by persistent vomiting. Vomiting blood or blood in the stool are serious indicators.
Other bleeding manifestations include bleeding from the gums or nose, or bleeding under the skin, which may resemble bruising. Rapid breathing suggests potential respiratory distress due to fluid accumulation. Individuals may also experience extreme fatigue, lethargy, or restlessness and irritability. Cold, clammy skin, along with a sudden drop in temperature and decreased urination, require immediate medical attention.
Treatment and Potential Complications
There is no specific antiviral treatment for dengue or severe dengue; medical management is supportive and focuses on addressing symptoms and complications. Maintaining proper fluid balance is a primary concern, often involving intravenous fluid therapy with crystalloid solutions. These fluids help restore circulating blood volume and prevent dehydration and low blood pressure.
Close monitoring of vital signs and laboratory parameters, such as hematocrit levels and platelet counts, is performed in a hospital setting. For severe bleeding, blood transfusions may be necessary to replace lost blood and improve oxygen delivery to tissues. Prophylactic platelet transfusions are not recommended for patients without active bleeding.
Severe dengue can lead to complications such as dengue shock syndrome (DSS), characterized by low blood pressure and multi-organ dysfunction. Other complications include severe bleeding, often in the gastrointestinal tract, and severe organ impairment, such as liver failure, myocarditis (heart inflammation), and encephalitis (brain inflammation). Prompt recognition and supportive care are important to reduce fatality rates.
Preventing Severe Dengue
Preventing dengue infection is the most effective way to prevent severe dengue. This involves comprehensive mosquito control measures, as the Aedes aegypti mosquito is the main vector. Eliminating mosquito breeding sites, such as standing water in containers, tires, and flower pots, is a fundamental strategy. Using insect repellents and wearing protective clothing, especially during peak mosquito activity hours, can also help reduce bites.
Vaccines are available in some regions, but their use comes with specific recommendations. Dengvaxia (CYD-TDV) is approved for individuals aged 9-45 years living in endemic areas. However, it is recommended only for those with a prior dengue infection, as administering it to individuals who have never had dengue can increase the risk of severe disease if they later become infected. Another vaccine, Q-denga® (TAK-003) is recommended by the WHO for children aged 6–16 years in settings with high dengue transmission. Early recognition of dengue symptoms and seeking medical care promptly are important, as early management can prevent progression.