Dengue fever

Dengue fever
Name	Dengue fever
Synonyms	Breakbone fever
Caption	The Aedes aegypti mosquito is the primary vector.
Field	Infectious disease
Symptoms	Fever, headache, muscle and joint pain, rash
Complications	Dengue hemorrhagic fever, Dengue shock syndrome
Onset	3–14 days after exposure
Duration	2–7 days
Causes	Dengue virus (DENV) spread by mosquitoes
Risks	Travel in tropical and subtropical regions
Diagnosis	Detection of antibodies to the virus or its RNA
Prevention	Mosquito control, Dengue vaccine
Treatment	Supportive care (oral rehydration, analgesics)
Medication	No specific antiviral
Prognosis	Usually good; risk in severe forms
Frequency	~400 million infections/year
Deaths	~40,000/year

Dengue fever. It is a mosquito-borne tropical disease caused by the Dengue virus. The disease is transmitted by several species of mosquito within the genus Aedes, principally Aedes aegypti. Symptoms typically begin three to fourteen days after infection and include high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash. A small proportion of cases develop into the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets, and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.

Signs and symptoms

The clinical course follows a characteristic pattern, often described as having three phases: febrile, critical, and recovery. The initial febrile phase involves a sudden high fever, often reaching 40°C (104°F), and is typically accompanied by generalized pain, headache, and a transient rash. Patients may experience pain behind the eyes, known as retro-orbital pain, and mild bleeding manifestations such as petechiae. This phase usually lasts two to seven days. The critical phase, which follows defervescence, is where plasma leakage may occur, leading to ascites and pleural effusion, hallmarks of severe disease. If severe, this can progress to hypovolemic shock and metabolic acidosis. The recovery phase sees the reabsorption of leaked fluid, which can lead to pulmonary edema if managed improperly. Other complications can include hepatitis, myocarditis, and encephalitis.

Cause

The illness is caused by infection with one of four closely related but antigenically distinct serotypes of the Dengue virus, designated DENV-1, DENV-2, DENV-3, and DENV-4. These are single-stranded RNA viruses belonging to the genus Flavivirus within the family Flaviviridae. The primary vector for transmission is the female Aedes aegypti mosquito, though Aedes albopictus can also act as a vector. The virus circulates in the blood of an infected person for two to seven days, during which time a feeding mosquito can acquire the virus. After an extrinsic incubation period of eight to twelve days, the mosquito can then transmit the virus to other humans through subsequent bites. The World Health Organization classifies it as a major arboviral disease.

Diagnosis

Diagnosis is primarily based on clinical presentation in endemic areas, but laboratory confirmation is essential. The World Health Organization provides case definitions for suspected, probable, and confirmed cases. Diagnostic methods include viral isolation in cell cultures, such as those from Aedes albopictus cells (C6/36 line), detection of viral RNA by nucleic acid amplification tests like reverse transcription polymerase chain reaction (RT-PCR), or detection of viral antigens such as the NS1 antigen test. Serological tests, including enzyme-linked immunosorbent assay (ELISA), can detect the presence of anti-dengue immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies. Interpretation is complicated by cross-reactivity with other flaviviruses, such as Zika virus and yellow fever virus.

Prevention

Prevention depends entirely on control of the mosquito vectors and protection from bites. Key strategies include environmental management to eliminate breeding sites, such as covering water storage containers and applying larvicides like temephos. Personal protection involves using mosquito nets, wearing protective clothing, and applying insect repellent containing DEET or picaridin. Community-based integrated vector management programs are promoted by the World Health Organization. The first licensed vaccine, Dengvaxia (CYD-TDV) by Sanofi Pasteur, is approved in several endemic countries but has specific recommendations due to its profile, which indicates a risk of severe disease in seronegative individuals. Other vaccine candidates, like those from Takeda Pharmaceutical Company and the Butantan Institute, are under development.

Management

No specific antiviral therapy exists; treatment is supportive and based on symptom management. For mild to moderate disease, adequate oral fluid intake and analgesics like acetaminophen (paracetamol) are recommended, while nonsteroidal anti-inflammatory drugs like ibuprofen and aspirin are avoided due to bleeding risk. For severe dengue, careful fluid management with crystalloids or colloids is critical to prevent shock while avoiding fluid overload. Blood transfusion with platelets or fresh frozen plasma may be necessary in cases of significant hemorrhage. Patients require close monitoring of hematocrit, platelet count, and vital signs, often in settings like an intensive care unit. The World Health Organization provides detailed guidelines for triage and management.

Epidemiology

It is the most prevalent mosquito-borne viral disease in humans, with an estimated 400 million infections annually across more than 100 countries in tropical and subtropical regions of the Asia-Pacific, the Americas, Africa, and the Caribbean. Major outbreaks have occurred in Brazil, the Philippines, India, and Bangladesh. The incidence has increased dramatically over recent decades due to factors including unplanned urbanization, increased international travel, and climate change affecting mosquito habitats. The Centers for Disease Control and Prevention and the European Centre for Disease Prevention and Control monitor its spread. Severe disease is more common in secondary infections with a different serotype, a phenomenon linked to antibody-dependent enhancement.

Category:Flaviviruses Category:Tropical diseases Category:Insect-borne diseases