Arbovirus (arthropod-borne virus) is defined as any virus that is transmitted to humans and/or other vertebrates by certain species of blood-feeding arthropods, mostly insects (flies and mosquitoes) and arachnids (ticks). Arbovirus is a descriptive term based on transmission by vectors with particular characteristics. It is not part of the International Committee on Taxonomy of Viruses classification of viruses (ie, it is not a species, genus, or family), which is based on the nature and structure of the viral genome.
Families in the current classification system that have some arbovirus members include
Peribunyaviridae
Flaviviridae
Orthomyxoviridae (eg, thogotoviruses)
Sedorreoviridae (eg, orbiviruses)
Togaviridae (alphaviruses)
(See International Committee on Taxonomy of Viruses: Current ICTV Taxonomy Release.)
Pearls & Pitfalls
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Most viruses associated with hemorrhagic fevers are classified in the families Arenaviridae and Filoviridae. However, some arboviruses, such as 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. Most arboviruses are transmitted by mosquitoes, but some are transmitted by ticks, and one (Oropouche virus) is transmitted by midges. 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 from nonhuman reservoirs, but most arboviral diseases are not transmissible by humans, perhaps because the typical viremia is inadequate to infect the arthropod vector. Exceptions include dengue, yellow fever, Zika virus infection, and chikungunya disease, which can be transmitted from person to person via mosquitoes. When human-to-human transmission occurs, it can be by blood transfusion, organ transplantation, sexual contact, and from mother to child during birth depending on the specific virus involved. Human-to-human transmission of most arboviruses through casual, everyday contact has not been documented.
Zika virus can be transmitted during sexual activity, whether the infected individual is asymptomatic or symptomatic.
Some infections (eg, West Nile virus infection, Colorado tick fever, dengue, Zika virus) have been shown to spread by blood transfusion or organ donation.
The Arenaviridae includes lymphocytic choriomeningitis virus, Lassa fever virus, Mopeia virus, Tacaribe virus, Junin virus, Lujo virus, and Machupo 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.
Laboratory diagnosis often involves viral cultures, polymerase chain reaction, electron microscopy, and antigen and antibody detection methods where available.
Treatment
Supportive care
Treatment for most of these infections is supportive.
Lassa fever, Rift Valley feverhemorrhagic fever with renal syndrome is present.
Prevention
Vector control
Prevention of vector bites
Sometimes vaccination
Avoidance of contact with infected animals, their products, and their excrement (hantaviruses)
The abundance and diversity of arboviruses means that it is often easier and cheaper to control arbovirus infections by destroying their arthropod vectors or taking other population control measures, preventing bites, and eliminating their breeding habitats than by developing specific vaccines or drug treatments.
Vector control and bite prevention
Diseases transmitted by mosquitoes or ticks can often be prevented by the following:
Reduce or limit infection in vector populations
Wear clothing that covers as much of the body as possible
Minimize the likelihood of exposure to the insect or tick (eg, for mosquitoes, limiting time outdoors in wet areas; for ticks, see sidebar Tick Bite Prevention)
There has been progress in reducing populations of Aedes aegypti mosquitoes through the release of sterile males or genetically modified males (1). Another approach is to limit infection among vector populations. Field trials are underway with introduction into the wild of Aedes aegypti that have been infected with Wolbachia bacteria, which blocks arbovirus midgut infection (see CDC: Mosquitoes with Wolbachia for reducing numbers of Aedes aegypti mosquitoes). These bacteria do not reduce mosquito populations. Instead, they block infection of the mosquitoes by dengue, chikungunya, and Zika viruses, thus reducing transmission of disease. The Wolbachia are transmitted to the infected mosquito's offspring, thus multiplying the effectiveness of the technique.
Diseases transmitted by rodent excreta can be prevented by the following:
Before cleaning, ventilate for ≥ 15 minutes closed spaces where mice have been.
Wet down surfaces with a 10% bleach solution before sweeping or cleaning.
Avoid stirring up dust.
Seal sites of potential rodent entry into homes and nearby buildings.
Prevent rodent access to food.
Eliminate potential nesting sites in and around the home and other buildings.
Guidelines for cleaning up after rodents and working in areas with potential rodent excreta are available from the Centers for Disease Control and Prevention (CDC).
Because transmission of the filoviruses Ebola virus and Marburg virus is predominantly from person to person, prevention of spread requires strict quarantine and isolation measures.
Vaccination
At present, in the United States, there are effective vaccines only for Ebola virus, yellow fever virus, Japanese encephalitis virus, and tick-borne encephalitis. Vaccines for dengue are available, but efficacy is only moderate and varies by dengue immune status, serotype, and patient age; studies are ongoing. The vaccine is approved in the United States for people ages 9 through 16 who have laboratory-confirmed previous dengue infection and who live in endemic areas.
Reference
1. Martín-Park A, Che-Mendoza A, Contreras-Perera Y, et al: Pilot trial using mass field-releases of sterile males produced with the incompatible and sterile insect techniques as part of integrated Aedes aegypti control in Mexico. PLoS Negl Trop Dis 16(4):e0010324, 2022. Published 2022 Apr 26. doi:10.1371/journal.pntd.0010324
