Dengue is a self-limited, systemic viral infection transmitted between humans by mosquitoes. The rapidly expanding dengue is a public health challenge with an economic burden that is currently unmet by licensed vaccines, specific therapeutic agents and efficient vector-control strategies.
Clinical Manifestations of Dengue fever:
After an incubation period of 3 to 7 days, the initial febrile phase is typically characterized by high fever associated with headache, vomiting, myalgias (body aches), and joint pain, sometimes with a transient macular rash. Children have high fever but are usually less symptomatic than adults during this phase of the illness. Other symptoms include mild hemorrhagic manifestations such as petechiae and bruising, particularly at venipuncture sites. Liver is palpable most of the times. This phase lasts for 3 to 7 days, after which most patients recover without complications.
Laboratory findings include mild-to-moderate thrombocytopenia and leukopenia, often with a moderate elevation of hepatic aminotransferase levels.Hematocrit is sometimes increased which is a grave sign as it indicates extravasation of fluid from the blood vessels.
Symptoms of dengue:
In a small proportion of patients, typically in children and young adults, a systemic vascular leak syndrome becomes evident by increasing hemoconcentration, hypoproteinemia, pleural effusions, and ascites. Once hypotension develops, systolic pressure decreases rapidly and irreversible shock and death may occur despite aggressive attempts at resuscitation. Signs of deterioration include persistent vomiting, severe abdominal pain, tender hepatomegaly, a high or increasing hematocrit level that is accompanied with a rapid decrease in the platelet count, serosal effusions, mucosal bleeding, and lethargy or restlessness. Hemorrhagic manifestations are most common during this critical period which include major skin bleeding, mucosal bleeding (gastrointestinal or vaginal) with no obvious precipitating factors and only minor plasma leakage. Moderate-to-severe thrombocytopenia is common, and a transient increase in the activated partial-thromboplastin time and a decrease in fibrinogen levels are also noted.
Diagnosis of Dengue Fever:
Laboratory diagnosis of dengue is established directly by detection of viral components in serum or indirectly by serologic means. During the febrile phase, detection of viral nucleic acid in serum by means of reverse-transcriptase–polymerase-chain-reaction assay or detection of the virus-expressed soluble nonstructural protein 1 (NS1) is sufficient for a confirmatory diagnosis. For primary infections in persons who have not received treatment previously (travelers), the diagnostic sensitivity of NS1 detection in the febrile phase is upto 90%, and antigenemia may persist for several days after the resolution of fever. The sensitivity of NS1 detection in the febrile phase is lower in secondary infections (60 to 80%). Serologic diagnosis of dengue relies on the detection of high levels of serum IgM that bind dengue virus antigens; IgM can be detected as early as 4 days after the onset of fever.
Management of Dengue Fever:
No effective antiviral agents to treat dengue infection are currently available, and treatment remains supportive, with particular emphasis on careful fluid management. Development of any warning sign indicates the need for hospitalization and close observation, with administration of parenteral fluids in patients with inadequate oral intake or a rapidly increasing hematocrit. If the condition progresses to the dengue shock syndrome, prompt fluid resuscitation to restore plasma volume is necessary, followed by ongoing fluid therapy to support the circulation at a level just sufficient to maintain critical organ perfusion. Blood transfusion can be lifesaving for patients with severe bleeding, but it should be undertaken with care because of the risk of fluid overload.