What Is Dengue?
The world's most common arthropod-borne virus disease is dengue, which is spread by mosquitoes. It is also called "breakbone fever," "dandy fever," or "seven-day fever" because of how long the symptoms typically last. Severe sickness and death are possible, even though the majority of cases are asymptomatic. Aedes mosquitoes are prevalent in tropical and subtropical regions and carry the virus. Dengue has become endemic in many areas of the world due to a sharp rise in incidence over the previous few decades. With almost 100 million cases each year, the virus spreads the quickest in the world through mosquitoes.
More than 100 nations are home to dengue, which also results in 20 to 25,000 fatalities, most of them in children. Australia, Asia, Africa, and the Americas all experience annual epidemics. Female mosquitoes belonging to the Aedes aegypti and Aedes albopictus mosquito species are the main carriers of the disease. A. albopictus is linked to a growing range, can withstand colder temperatures better, feeds aggressively but seldom, and may be related to increased numbers despite A. aegypti being linked to most infections. During the day, these mosquito species are active and typically reside indoors. Transfusions of blood, breast milk, and organs have all been documented as ways of transmission during perinatality.
As much as 75 percent of human infections are asymptomatic. It is possible to witness a range of illnesses, from bleeding and shock to self-limiting dengue fever. Severe dengue fever develops in 0.5 percent to five percent of cases of illness. Rates of death could surpass 20 percent in the absence of appropriate care. It affects mostly the children. It might take three to ten days, although four to seven days is the usual incubation time. It is doubtful that dengue fever is the cause of symptoms that appear more than two weeks after exposure.
What Are the Symptoms of Dengue?
Dengue has three stages: critical, febrile, and recovery. An abrupt, high-grade fever, often lasting two to seven days, occurs during the febrile phase, with a temperature of about 40 degrees Celsius. Facial flushing, skin erythema, myalgias, arthralgias, headache, sore throat, injection of the conjunctiva, anorexia, nausea, and vomiting are among the associated symptoms. The initial one to two days of fever and the last day is when a general blanchable macular rash appears in cases of skin erythema. A secondary maculopapular rash may appear within 24 hours. Warning symptoms appear, the hematocrit rises, and the platelet count rapidly drops, signaling the start of the critical phase. Shock, organ failure, disseminated intravascular coagulation, or bleeding are possible outcomes. In two to three days, extravascular fluid will gradually be reabsorbed throughout the healing phase. At this point, the patient will show signs of bradycardia.
What Are the Diagnostic Tests for Dengue?
1. Clinical Assessment: Diagnosis of dengue often begins with a thorough clinical evaluation by a healthcare provider. Symptoms typically include sudden onset of fever, severe headache, retro-orbital pain, muscle and joint pain (myalgia and arthralgia), rash, and occasionally minor bleeding manifestations like petechiae or gum bleeding. The clinical presentation can vary widely and may mimic other febrile illnesses like malaria or influenza.
2. Laboratory Tests:
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Dengue NS1 Antigen Test: This test detects the presence of the dengue virus NS1 antigen in the blood during the acute phase of infection, typically within the first week of illness. NS1 antigen is secreted by the virus-infected cells and can be detected using enzyme-linked immunosorbent assay (ELISA) or rapid diagnostic tests (RDTs). It provides a rapid and specific diagnosis.
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Dengue IgM and IgG Antibody Tests: Dengue-specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies can be detected in the blood during different stages of the illness. IgM antibodies usually appear towards the end of the first week of illness and persist for two to three months, while IgG antibodies develop later and can persist for years. Serological tests like ELISA or rapid tests detect these antibodies and are particularly useful in diagnosing secondary dengue infections.
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Dengue PCR (Polymerase Chain Reaction): PCR assays can directly detect the viral RNA in the blood during the early stages of infection, even before the appearance of antibodies. PCR is highly sensitive and specific but may not be widely available in resource-limited settings.
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Complete Blood Count (CBC): Blood tests, including CBC, may reveal leukopenia (low white blood cell count) and thrombocytopenia (low platelet count), which are common findings in dengue fever. Platelet count is particularly important as severe thrombocytopenia can indicate a higher risk of bleeding complications.
3. Imaging Studies: In severe cases of dengue fever, complications such as plasma leakage leading to dengue shock syndrome or severe organ involvement like liver dysfunction or central nervous system manifestations may occur. Imaging studies such as abdomen ultrasound or chest X-rays may be performed to assess fluid accumulation in body cavities or identify other complications.
4. Other Tests: In cases where dengue infection is suspected but not confirmed by initial tests, repeat testing after a few days may be necessary due to the transient nature of viral markers in the blood. Tests to rule out other common febrile illnesses such as malaria, chikungunya, or Zika virus may be warranted depending on the clinical presentation and epidemiological context.
Conclusion
Diagnosing dengue involves a multifaceted approach, combining clinical assessment and laboratory tests. Key components include rapid antigen tests like NS1 detection and serological tests for IgM and IgG antibodies. PCR assays offer early detection, while CBC aids in identifying hematological abnormalities. Prompt and accurate diagnosis is critical for appropriate management and preventing complications. Given the overlapping symptoms with other febrile illnesses, comprehensive testing and clinical evaluation are essential for timely intervention and reducing the burden of dengue fever.
