Important Arboviruses and Their Vectors

Arboviruses are viruses transmitted between vertebrate hosts by infected arthropods, especially mosquitoes and ticks. Their transmission, animal reservoirs and clinical effects vary widely, making vector identification and surveillance important for prevention and public health preparedness.

Understanding Arboviruses

Arboviruses are grouped by their mode of transmission, not by a single taxonomic family. In a biological transmission cycle, a vector acquires a virus while feeding on an infected host. After the virus replicates in the vector during an extrinsic incubation period, the vector can transmit it to another susceptible host.

• Most arboviruses are RNA viruses and belong to several families, including Flaviviridae, Togaviridae, Peribunyaviridae, Phenuiviridae, Nairoviridae and Reoviridae.
• The main vectors are mosquitoes and ticks; biting midges and sandflies also transmit some arboviruses.
• Transmission cycles may involve humans, livestock, birds or other vertebrates. Some infections cause mild fever, while others can cause severe neurological or haemorrhagic disease.

Families and Important Diseases

• Flaviviridae: Includes the genus Flavivirus and important human pathogens such as Dengue, Yellow Fever, Zika, Japanese Encephalitis (JE), West Nile and Kyasanur Forest Disease (KFD) viruses.
• Togaviridae: Includes the genus Alphavirus, which contains Chikungunya virus.
• Peribunyaviridae: Includes the genus Orthobunyavirus. Shamonda virus belongs to this genus and the Simbu serogroup.
• Phenuiviridae and Nairoviridae: Rift Valley Fever virus is a phlebovirus in Phenuiviridae; Crimean-Congo Haemorrhagic Fever (CCHF) virus belongs to the genus Nairovirus in Nairoviridae.
• Reoviridae: Includes Orbivirus, which causes livestock diseases such as Bluetongue and African Horse Sickness.

Major Arboviruses, Vectors and Hosts

• Dengue: Caused by a Flavivirus and transmitted mainly by Aedes aegypti and Aedes albopictus. It occurs widely in tropical and subtropical regions; severe disease can involve haemorrhage and shock.
• Chikungunya: An Alphavirus spread by Aedes mosquitoes, particularly A. aegypti and A. albopictus. Fever and often severe joint pain are characteristic.
• Zika: A Flavivirus primarily transmitted by Aedes mosquitoes. Infection during pregnancy is associated with microcephaly and other severe fetal brain defects; Guillain-Barré syndrome can occur in adults. Sexual and mother-to-fetus transmission are also possible.
• Japanese Encephalitis: A Flavivirus transmitted by Culex mosquitoes, especially Culex tritaeniorhynchus. Wading birds and pigs are important hosts. Severe infection can cause encephalitis; a vaccine is available.
• Yellow Fever: A Flavivirus transmitted by Aedes and Haemagogus mosquitoes. It has sylvatic (jungle), intermediate (savanna) and urban transmission cycles. The name refers to jaundice in some patients; vaccination provides lifelong protection.
• West Nile: A Flavivirus transmitted mainly by Culex mosquitoes, with birds as the primary reservoir hosts. Most human infections are asymptomatic, but severe cases can cause encephalitis or meningitis.
• Rift Valley Fever: A phlebovirus in Phenuiviridae, transmitted mainly by mosquitoes, including floodwater Aedes. It affects livestock such as sheep, cattle and goats, causing abortions and high mortality. People can be infected through mosquito bites or contact with infected animal tissues or fluids.
• CCHF: Caused by a Nairovirus and transmitted by Hyalomma ticks. Livestock can act as amplifying hosts; infection in humans may cause severe haemorrhagic fever.
• KFD: A Flavivirus transmitted mainly by the hard tick Haemaphysalis spinigera. Endemic to southwestern India, particularly Karnataka, it affects monkeys, rodents and humans and can cause haemorrhagic fever.
• Shamonda: An insect-borne Orthobunyavirus in Peribunyaviridae, of the Simbu serogroup. It primarily affects livestock, particularly cattle; it has also been detected in sheep, goats, horses and alpacas. Culicoides biting midges are its vector.
• Chandipura: The source identifies this virus as an Orthobunyavirus associated with sandfly transmission and acute encephalitis syndrome, particularly in children. It has been reported in parts of India and Africa.

Vectors and Disease Control

• Aedes mosquitoes: Important vectors of Dengue, Chikungunya, Zika and Yellow Fever. They can breed in water collected in artificial containers, making removal of breeding sites a key control measure.
• Culex mosquitoes: Transmit JE and West Nile virus and commonly breed in stagnant water. Some Anopheles species can also transmit arboviruses.
• Ticks: Hard ticks (family Ixodidae) transmit KFD and CCHF and can act as vectors and reservoirs. Soft ticks (family Argasidae) are less commonly associated with arboviruses.
• Biting midges: Culicoides species transmit livestock viruses, including Bluetongue and Shamonda.
• Sandflies: Phlebotomus species are associated with Chandipura virus in the source text and also transmit Leishmaniasis.
• Prevention: Vector control combines removal of breeding sites, environmental management and insecticides, including larvicides and adulticides. Repellents, protective clothing and mosquito nets help reduce human exposure.
• Preparedness: Surveillance of vectors and disease in humans and animals supports early detection and response. Vaccines are available for Yellow Fever and JE; research continues on vaccines for other arboviral diseases.

Key Prelims Takeaways

• “Arbovirus” is an ecological grouping based on arthropod transmission, not a taxonomic classification.
• Aedes mosquitoes transmit Dengue, Chikungunya and Zika; Culex mosquitoes transmit JE and West Nile virus.
• Yellow Fever virus has sylvatic, intermediate and urban transmission cycles; an effective vaccine provides lifelong protection.
• Haemaphysalis spinigera transmits KFD, while Hyalomma ticks transmit CCHF.
• Shamonda is an Orthobunyavirus in Peribunyaviridae; its vector is the Culicoides biting midge.
• Vector control, personal protection and surveillance in humans and animals are central to arbovirus prevention and preparedness.

Recent Context

On October 22, 2026, France confirmed its first human Shamonda virus case; the severely immunocompromised patient died. The likely exposure was a midge bite in eastern France, where the virus had circulated in animals. Authorities reported no identified risk to the general population and notified WHO and ECDC.