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Arthropod-borne viruses (arboviruses) are transmitted between vertebrate hosts by certain species of hematophagous insects, including mosquitoes, sand flies, midges, and ticks.1 Although covered by the overarching term, “arbovirus,” to denote the mode of transmission, these viruses belong to different taxonomic families. Transmission by arthropod vectors is biologic, rather than mechanical, in that true arboviruses replicate in arthropod tissues and salivary glands prior to transmission, rather than simply being carried by vectors.

Arbovirus infections in natural hosts typically result in development of a viremia of sufficient magnitude to infect an arthropod and propagate further vector-borne transmission. For most arboviruses, humans are not the natural host in which they ordinarily reside and propagate, and the majority of human infections do not produce clinical disease. However, in the small proportion of infected persons with clinically apparent illness, presentation typically falls into the following broad categories: generalized febrile illness, neuroinvasive disease, polyarthralgia, or hemorrhagic fever. Development of severe, possibly fatal, disease is rare and often dependent on age and underlying medical conditions. Described in separate chapters are the related diseases of dengue, Zika, chikungunya (chapter141), and arthropod-borne viral hemorrhagic fevers (Chapter 139).


Medically important arboviruses belong primarily to Flaviviridae, Togaviridae, Peribunyaviridae, Phenuiviridae, and Reoviridae families (Table 142-1). The term arbovirus covers a heterogeneous group of viruses with only broad commonalities in mode of transmission but some significant differences in viral replication strategies, ecologic dynamics, and infection outcomes. The most comprehensive list of viruses biologically transmitted by arthropods in nature and infectious for humans or domestic animals is contained in the International Catalogue of Arboviruses.2 Of more than 500 viruses listed, just over 100 have been shown to cause disease in humans and only a small proportion of those are of clinical or public health importance.3


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