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Arbovirus (arthropod-borne virus) is a term applied to a group of viruses that are transmitted to vertebrates by certain types of blood-eating insects, chiefly mosquitoes and ticks (arthropods). Arbovirus is not part of the current viral classification system. Families in the current classification system that have some arbovirus members include
Arenaviridae and Filoviridae (including Marburg and Ebola viruses) are not arboviruses.
Arboviruses number > 250 and are distributed worldwide; at least 80 cause human disease. Birds are often reservoirs for arboviruses, which are transmitted by mosquitoes to horses, other domestic animals, and humans. Most arboviral diseases are not transmissible by humans, perhaps because the typical viremia is inadequate to infect the arthropod vector; an exception is dengue fever, which can be transmitted from person to person via mosquitoes. Some infections (eg, West Nile virus, Colorado tick fever) can be spread by blood transfusion or organ donation. Reservoirs for Bunyaviridae include insects and vertebrates, often rodents. These viruses spread to humans directly from their reservoirs, but human-to-human transmission may occur.
Arenaviruses are usually transmitted by rodents and their excreta; in the case of Lassa fever, human-to-human transmission is possible.
Reservoirs for the Marburg and Ebola viruses are unknown, and human-to-human transmission occurs readily.
Many infections are asymptomatic. When symptomatic, they generally begin with a minor nonspecific flu-like illness that may evolve to one of a few syndromes (see Table 1: Arboviridae, Arenaviridae, and Filoviridae: Arbovirus, Arenavirus, and Filovirus Diseases ). These syndromes include lymphadenopathy, rashes, aseptic meningitis, encephalitis, arthralgias, arthritis, and noncardiogenic pulmonary edema. Many cause fever and bleeding tendencies (hemorrhagic fever). Decreased synthesis of vitamin K–dependent coagulation factors, disseminated intravascular coagulation, and altered platelet function contribute to bleeding.
Laboratory diagnosis often involves viral cultures, PCR, electron microscopy, and antigen and antibody detection where available.
Treatment
Treatment for most of these infections is supportive. In hemorrhagic fevers, bleeding may require phytonadione (see Vitamin Deficiency, Dependency, and Toxicity: Treatment under Vitamin K Deficiency). Transfusion of packed RBCs or fresh frozen plasma may also be necessary. Aspirin and other NSAIDs are contraindicated because of antiplatelet activity.
Ribavirin 30 mg/kg IV (maximum, 2 g) loading dose followed by 16 mg/kg IV (maximum, 1 g/dose) q 6 h for 4 days, then 8 mg/kg IV (maximum, 500 mg/dose) q 8 h for 6 days is recommended for hemorrhagic fever caused by arenaviruses or bunyaviruses including Lassa fever, Rift Valley fever, and Crimean-Congo hemorrhagic fever. For dosage in hemorrhagic fever with renal syndrome, see Arboviridae, Arenaviridae, and Filoviridae: Prognosis. Antiviral treatment for other syndromes has not been adequately studied.
Prevention
Diseases transmitted by mosquitoes or ticks can often be prevented by wearing clothing that covers as much of the body as possible, using insect repellants, and minimizing the likelihood of exposure to the insect (eg, for mosquitoes, limiting time outdoors in wet areas; for ticks, see Sidebar 1: Rickettsiae and Related Organisms: Tick Bite Prevention ).
Diseases transmitted by rodent excreta can be prevented by sealing sites of potential rodent entry into homes and nearby buildings, preventing rodent access to food, and eliminating potential nesting sites around the home. Guidelines for cleaning and working in areas with potential rodent excreta are available through the Centers for Disease Control and Prevention (CDC).
Last full review/revision December 2009 by Kenneth M. Kaye, MD
Content last modified December 2009
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