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

• Bunyaviridae (including bunyaviruses, phleboviruses, nairoviruses, and hantaviruses)
• Flaviviridae (including flaviviruses)
• Reoviridae (including coltiviruses and orbiviruses)
• Togaviridae (including alphaviruses)

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.

Table 1
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Arbovirus, Arenavirus, and Filovirus Diseases Distinguishing Symptoms Viral Agent or Disease Family Vector Major Distribution Fever, malaise, headaches, myalgias Additional features: none Colorado tick fever Reoviridae (Coltivirus) Tick Western US, western Canada Phlebotomus fever Bunyaviridae (Phlebovirus) Sand fly Mediterranean basin, Balkans, Middle East, Pakistan, India, China, eastern Africa, Panama, Brazil Venezuelan equine encephalitis Togaviridae (Alphavirus) Mosquito Argentina, Brazil, northern South America, Panama, Mexico, Florida Rift Valley fever* Bunyaviridae (Phlebovirus) Mosquito South Africa, eastern Africa, Egypt Lymphadenopathy, rash Dengue fever Flaviviridae Mosquito Southeast Asia, Africa, Oceania, Australia, South America, Mexico, Caribbean, US West Nile fever Flaviviridae Mosquito Africa, Middle East, southern France, former Soviet Union, India, Indonesia, US Arthralgia, rash Chikungunya disease Togaviridae (Alphavirus) Mosquito Africa, India, Guam, Southeast Asia, New Guinea, limited areas of Europe Mayaro virus Togaviridae (Alphavirus) Mosquito Brazil, Bolivia, Trinidad Ross River virus Togaviridae (Alphavirus) Mosquito Australia, New Guinea, Solomon Islands, Samoa, Cook Islands Barmah Forest virus Togaviridae (Alphavirus) Mosquito Australia Sindbis virus disease (Ockelbo disease, Karelian fever) Togaviridae (Alphavirus) Mosquito Africa, Australia, former Soviet Union, Finland, Sweden Hemorrhagic signs† Yellow fever Flaviviridae Mosquito Central and South America, Africa Dengue hemorrhagic fever Flaviviridae Mosquito Southeast Asia, Oceania, Caribbean Kyasanur Forest disease Flaviviridae Tick India Omsk hemorrhagic fever Flaviviridae Tick Former Soviet Union Crimean-Congo hemorrhagic fever Bunyaviridae (Nairovirus) Tick Africa, southern and eastern Europe, India, China, Middle East, former Soviet Union Hantaan virus Bunyaviridae (Hantavirus) Rodent Korea, Japan, China, Southeast Asia, Europe Seoul virus Bunyaviridae (Hantavirus) Rodent Korea, Japan Puumala virus (nephropathia epidemica) Bunyaviridae (Hantavirus) Rodent Scandinavia, former Soviet Union Machupo virus Arenaviridae Rodent Bolivia Junin virus Arenaviridae Rodent Argentina Guanarito virus Arenaviridae Rodent Venezuela Lassa fever Arenaviridae Rodent, human to human West Africa Marburg virus Filoviridae Unknown, human to human Zimbabwe, Kenya, Uganda Ebola virus Filoviridae Unknown, human to human Zaire, Sudan Noncardiogenic pulmonary edema Hantavirus: Sin Nombre, Black Creek Canal, Bayou, New York-1, Rio Mamore Bunyaviridae (Hantavirus) Rodent US (west of Mississippi River), Canada, Brazil, Bolivia, Paraguay, Argentina Fever and CNS involvement Eastern equine encephalitis Togaviridae (Alphavirus) Mosquito Atlantic and Gulf coasts of US, Caribbean, upper New York, western Michigan Western equine encephalitis Togaviridae (Alphavirus) Mosquito US, Canada, Central and South America West Nile virus Flaviviridae Mosquito Africa, Middle East, southern France, former Soviet Union, India, Indonesia, US St. Louis encephalitis Flaviviridae Mosquito US, Caribbean Venezuelan equine encephalitis Togaviridae (Alphavirus) Mosquito Argentina, Brazil, northern South America, Panama, Mexico, Florida La Crosse encephalitis Bunyaviridae Mosquito North Central States, New York Japanese encephalitis Flaviviridae Mosquito Japan, Korea, China, India, Philippines, Southeast Asia, former Soviet Union (eastern) Powassan virus Flaviviridae Tick Eastern Canada, New York Murray Valley encephalitis Flaviviridae Mosquito Australia, New Guinea Kyasanur Forest disease Flaviviridae Tick India Tick-borne encephalitis Flaviviridae Tick Europe, Balkans, former Soviet Union Lymphocytic choriomeningitis Arenaviridae Rodent US, Argentina, Germany, Balkans * Rift Valley fever also causes hemorrhage, meningoencephalitis, and ocular disorders. †The Seoul, Puumala, Dobrava, and Hantaan hantaviruses cause hemorrhagic fever with renal syndrome. Arbovirus, Arenavirus, and Filovirus Diseases Distinguishing Symptoms Viral Agent or Disease Family Vector Major Distribution Fever, malaise, headaches, myalgias Additional features: none Colorado tick fever Reoviridae (Coltivirus) Tick Western US, western Canada Phlebotomus fever Bunyaviridae (Phlebovirus) Sand fly Mediterranean basin, Balkans, Middle East, Pakistan, India, China, eastern Africa, Panama, Brazil Venezuelan equine encephalitis Togaviridae (Alphavirus) Mosquito Argentina, Brazil, northern South America, Panama, Mexico, Florida Rift Valley fever* Bunyaviridae (Phlebovirus) Mosquito South Africa, eastern Africa, Egypt Lymphadenopathy, rash Dengue fever Flaviviridae Mosquito Southeast Asia, Africa, Oceania, Australia, South America, Mexico, Caribbean, US West Nile fever Flaviviridae Mosquito Africa, Middle East, southern France, former Soviet Union, India, Indonesia, US Arthralgia, rash Chikungunya disease Togaviridae (Alphavirus) Mosquito Africa, India, Guam, Southeast Asia, New Guinea, limited areas of Europe Mayaro virus Togaviridae (Alphavirus) Mosquito Brazil, Bolivia, Trinidad Ross River virus Togaviridae (Alphavirus) Mosquito Australia, New Guinea, Solomon Islands, Samoa, Cook Islands Barmah Forest virus Togaviridae (Alphavirus) Mosquito Australia Sindbis virus disease (Ockelbo disease, Karelian fever) Togaviridae (Alphavirus) Mosquito Africa, Australia, former Soviet Union, Finland, Sweden Hemorrhagic signs† Yellow fever Flaviviridae Mosquito Central and South America, Africa Dengue hemorrhagic fever Flaviviridae Mosquito Southeast Asia, Oceania, Caribbean Kyasanur Forest disease Flaviviridae Tick India Omsk hemorrhagic fever Flaviviridae Tick Former Soviet Union Crimean-Congo hemorrhagic fever Bunyaviridae (Nairovirus) Tick Africa, southern and eastern Europe, India, China, Middle East, former Soviet Union Hantaan virus Bunyaviridae (Hantavirus) Rodent Korea, Japan, China, Southeast Asia, Europe Seoul virus Bunyaviridae (Hantavirus) Rodent Korea, Japan Puumala virus (nephropathia epidemica) Bunyaviridae (Hantavirus) Rodent Scandinavia, former Soviet Union Machupo virus Arenaviridae Rodent Bolivia Junin virus Arenaviridae Rodent Argentina Guanarito virus Arenaviridae Rodent Venezuela Lassa fever Arenaviridae Rodent, human to human West Africa Marburg virus Filoviridae Unknown, human to human Zimbabwe, Kenya, Uganda Ebola virus Filoviridae Unknown, human to human Zaire, Sudan Noncardiogenic pulmonary edema Hantavirus: Sin Nombre, Black Creek Canal, Bayou, New York-1, Rio Mamore Bunyaviridae (Hantavirus) Rodent US (west of Mississippi River), Canada, Brazil, Bolivia, Paraguay, Argentina Fever and CNS involvement Eastern equine encephalitis Togaviridae (Alphavirus) Mosquito Atlantic and Gulf coasts of US, Caribbean, upper New York, western Michigan Western equine encephalitis Togaviridae (Alphavirus) Mosquito US, Canada, Central and South America West Nile virus Flaviviridae Mosquito Africa, Middle East, southern France, former Soviet Union, India, Indonesia, US St. Louis encephalitis Flaviviridae Mosquito US, Caribbean Venezuelan equine encephalitis Togaviridae (Alphavirus) Mosquito Argentina, Brazil, northern South America, Panama, Mexico, Florida La Crosse encephalitis Bunyaviridae Mosquito North Central States, New York Japanese encephalitis Flaviviridae Mosquito Japan, Korea, China, India, Philippines, Southeast Asia, former Soviet Union (eastern) Powassan virus Flaviviridae Tick Eastern Canada, New York Murray Valley encephalitis Flaviviridae Mosquito Australia, New Guinea Kyasanur Forest disease Flaviviridae Tick India Tick-borne encephalitis Flaviviridae Tick Europe, Balkans, former Soviet Union Lymphocytic choriomeningitis Arenaviridae Rodent US, Argentina, Germany, Balkans * Rift Valley fever also causes hemorrhage, meningoencephalitis, and ocular disorders. †The Seoul, Puumala, Dobrava, and Hantaan hantaviruses cause hemorrhagic fever with renal syndrome.

Treatment

• Supportive care
• Sometimes ribavirinSome Trade Names
  VIRAZOLE
  Click for Drug Monograph
  

Treatment for most of these infections is supportive. In hemorrhagic fevers, bleeding may require phytonadioneSome Trade Names
MEPHYTON
Click for Drug Monograph
(see Vitamin Deficiency, Dependency, and Toxicity: Treatment under Vitamin K Deficiency). Transfusion of packed RBCs or fresh frozen plasma may also be necessary. AspirinSome Trade Names
BUFFERIN
ECOTRIN
GENACOTE
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and other NSAIDs are contraindicated because of antiplatelet activity.

RibavirinSome Trade Names
VIRAZOLE
Click for Drug Monograph
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 February 2012