There are at least 100 potential such viruses that infect humans. Some are global, whereas others have extremely limited geographical range (although they may be very important causes of encephalitis in those areas).
The most important of the arthropod vectors are mosquitoes (eg Dengue fever, West Nile virus). Ticks can also carry a variety of arboviruses (eg Tick-borne encephalitis). Some of the arboviruses can be transmitted directly from human to human eg Congo Crimean fever, Rift Valley fever.
Most arboviruses are zoonoses ie their usual reservoir is animals esp birds and rodents. These animals may not manifest much in the way of disease. However, spill over into another species may be triggered by changes in the ecology eg a new vector. If this species does manifest disease, it can be a warning of an impending epidemic. Dengue fever and O'nyong nyong are unique in having humans as their main reservoir.
There are 3 main patterns of disease:
- Fever, arthralgia, rash
- Haemorrhagic fever [arboviruses are not the only cause]
- Encephalitis +/- myelitis [can be polio-like]
Each arbovirus tends to present with only one of these patterns, but increasingly it appears that other presentations are possible.
Common Arboviruses causing human infection
- Dengue fever
- West Nile virus (WNV)
- Tick borne encephalitis (TBE)
- Yellow fever
- Japanese encephalitis
- Murray Valley fever
- Rift Valley fever
- O'nyong nyong
Some of the arboviruses associated with mammal spread disease and that infect man are listed below.
- Tick-borne encephalitis
- biting midges-borne (possibly none cause human disease)
- sandfly/mosquito-borne (possible none cause human disease)