BOURBON VIRUS

Arbovirus (arthropod-borne virus) applies to any virus that is transmitted to humans and/or other vertebrates by certain species of blood-feeding arthropods, chiefly insects (flies and mosquitoes) and arachnids (ticks). Arbovirus is not part of the current viral classification system, which is based on the nature and structure of the viral genome.

Families in the current classification system that have some arbovirus members include

Bunyaviridae (comprising the bunyaviruses, phleboviruses, nairoviruses, and hantaviruses)

Togaviridae

Flaviviridae (comprising only the flaviviruses)

Reoviridae (comprising the coltiviruses and orbiviruses)

Togaviridae (comprising the alphaviruses)

Pearls & Pitfalls

Arbovirus is not a family of viruses; the term indicates only that a virus is transmitted by certain species of arthropods—arthropod-borne virus.

Members of many different viral families may be arboviruses.

Most viruses associated with hemorrhagic fevers are classified in the families Arenaviridaeand Filoviridae. However, some flaviviruses (yellow fever, dengue viruses) and some Bunyaviridae (Rift Valley fever virus, Crimean-Congo hemorrhagic fever virus, severe fever with thrombocytopenia virus, the hantaviruses) may be associated with hemorrhagic symptoms.

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. Other reservoirs for arboviruses include arthropods and vertebrates (often rodents, monkeys, and humans). These viruses may spread to humans directly from nonhuman reservoirs, but human-to-human transmission may also occur. Most arboviral diseases are not transmissible by humans, perhaps because the typical viremia is inadequate to infect the arthropod vector; exceptions include dengue fever, yellow fever, Zika virus infection, and chikungunya disease, which can be transmitted from person to person via mosquitoes. Also, Zika virus can be transmitted during sexual activity from infected symptomatic or asymptomatic men to their sex partners (male or female) or from infected women to their sex partner.

Some infections (eg, West Nile virus infection, Colorado tick fever, dengue, Zika virus) have been spread by blood transfusion or organ donation.

The Arenaviridae includes lymphocytic choriomeningitis virus, Lassa fever virus, Mopeia virus, Tacaribe virus, Junin virus, Lujo virus, Machupo virus, and Guaroa virus; all are transmitted by rodents and thus are not arboviruses. Lassa fever virus can be transmitted from person to person.

The Filoviridae consists of 2 genera: Ebolavirus(consisting of 5 species) and Marburgvirus (consisting of 2 species). The specific vectors of these viruses have not been confirmed, but fruit bats are the prime candidates; thus, Filoviridae are not arboviruses. Human-to-human transmission of Ebola virus and Marburg virus occurs readily.

Many of these 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 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