Dengue virus

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Summary of Dengue virus

Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Dengue is a Flavivirus and is a linear, enveloped, single stranded, positive sense, RNA virus. Symptoms typically begin three to fourteen days after infection. This may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash. Recovery generally takes less than two to seven days. In a small proportion of cases, the disease develops 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.

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Dengue virus

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DENGUE VIRUS osms.it/dengue-virus PATHOLOGY & CAUSES ▪ Viral disease, mosquito transmission ▫ Characterized by febrile illness ▫ AKA break-bone fever ▪ Four serotypes ▫ DENV-1 through DENV-4 ▫ IgG response to speciﬁc type → lifetime immunity ▫ Limited, transient cross-protectivity across viral types ▪ Vector ▫ Primarily Aedes aegypti and A. albopictus Pathogenesis ▪ Aedes mosquito bite → dengue virus skin introduction → local infection, response → dissemination → viremia (2–6 days later) → circulating leukocyte infection (especially) monocytes → viral replication, release → fever RISK FACTORS ▪ Endemic area residence ▪ Recent travel COMPLICATIONS Severe dengue ▪ AKA dengue hemorrhagic fever ▪ Viremia → local hemorrhage → systemic hemorrhage → hemodynamic collapse → shock ▫ Dengue shock syndrome (rare complication—DENV-2 confers highest risk) ▪ Direct bone marrow infection → hematopoietic stem cell infection → ↓ megakaryocyte differentiation (among all other cell lines) → ↓ platelets formed ▫ ↓ Circulating lifetime: virus-antibody complex → circulating platelet adherence → complement destruction 392 OSMOSIS.ORG ▪ ▪ ▪ ▪ of virus-antibody complex → adherent platelet destruction Capillary leak ▫ Direct effect: viral endothelial cell infection → cellular dysfunction → tight junction widening → capillary leak ▫ Indirect: virus-infected monocytes, dendritic cells, mast cells → TNFalpha, IFN-gamma, IL-2, IL-8, vascular endothelial growth factor release, complement activation → ↑ capillary permeability Molecular mimicry ▫ Viral E protein antibody response → plasminogen cross-reaction → inefﬁcient coagulation cascade → hemorrhage Liver failure ▫ Direct viral infection → Kupffer cells, hepatocytes → apoptosis → hepatocellular necrosis, Councilman bodies ▫ Sever disease → shock → liver hypoperfusion → hepatocellular injury, death Central nervous system (CNS) involvement ▫ Rare, direct viral infection of brain parenchyma SIGNS & SYMPTOMS ▪ High-grade fever (> 38.5°C/101.3°F) ▪ Generalized pain ▫ Abdominal pain/tenderness, headache, joint pain, muscle pain, eye/retro-orbital pain ▪ Nausea/vomiting ▪ Mucosal bleeding ▪ Rash Severe symptoms and signs ▪ Severe bleeding ▪ Fluid accumulation → respiratory distress ▫ Ascites, pleural effusion

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Dengue virus

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A 27-year-old woman comes to the emergency department because of severe fever, nausea, and generalized muscle, and joint pain. Her temperature is 40°C (104°F). She says that she returned to the United States a week ago after spending two weeks in southeast Asia doing charity work. She received all recommended vaccines prior to travelling. Physical examination shows mild gingival bleeding and petechial rash on her thorax. Laboratory studies show:

Which of the following is the most likely diagnosis?

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