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Arboviruses (or arthropod-borne viruses) are a heterogeneous group of viruses that share the same usual route of entry into humans: via the bite of an infected mosquito, tick, sandfly, or other arthropod.1,2 The life cycle of most arboviruses is characterized by the ability of the virus to replicate in both an arthropod vector and a vertebrate “natural” host (usually birds or small mammals) and by transmission between these two organisms at the time of the arthropod’s bite (eFig. 305.1). This cycle leads to establishment or maintenance of the virus in a given ecosystem. Humans or domestic animals are only “incidental” hosts for many species of arboviruses, as infection in such hosts (although capable of causing disease) is often a dead-end for the virus due to viremia being too low or too transient to contribute to maintenance of the cycle of transmission. Some viruses are specific to a single genus or species of insect, while others are transmissible by multiple vectors. In addition, some arthropods are capable of transovarial transmission, wherein their eggs (which sometimes overwinter and hatch in spring) are infected with the virus, allowing viral maintenance in areas of colder climate.

eFigure 305.1.

Arbovirus transmission cycle.

(Source: Centers for Disease Control and Prevention. Division of Vector Borne Infectious Diseases. Accessed September 11, 2008.)

Arboviruses generally produce 1 of 4 clinical syndromes: (1) central nervous system (CNS) disease, (2) febrile illness with rash, (3) arthropathy, or (4) hemorrhagic fever syndrome.1 In North America, encephalitis is the most commonly diagnosed manifestation of arboviral infection, with several viruses producing sporadic disease as well as outbreaks of infection each year. Table 305-1 provides a list of arboviruses presenting with different symptom complexes, and details the vector, reservoir, distribution, incubation period, and the population most affected.

Table 305-1. Arboviruses of Importance in North America and Globally

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