Arboviruses (ARthropod-BOrne VIRUS) are a large group of viruses that are carried and spread by arthropods, most commonly blood-sucking insects and ticks. In the United States, arboviruses are spread mainly by infected mosquitoes. Birds are a major source of infection for mosquitoes, which can sometimes transmit the infection to other animals, and humans. An arbovirus natural cycle includes periods in two hosts:

The virus is picked up during a blood meal. It multiplies and eventually lodges in the arthropod's salivary glands, and is transmitted during any subsequent feeding. The arthropod can remain infective for life, without being harmed.

Many arboviral diseases are characterized by long periods of invisibility, when little or no evidence of their existence can be detected. At unpredictable intervals, sometimes separated by several decades, they suddenly reappear. Weather- and climate-related factors, and ecological disturbances such as the introduction of exotic species of mosquitoes or other insects into new habitats, and the expansion of human settlement into previously unpopulated areas, all increase the potential exposure of humans to arbovirus-borne diseases.

The table below lists some of the more common arboviral diseases.

Yellow Fever California Encephalitis Sandfly fever
St. Louis Encephalitis Eastern Equine Encephalitis Venezuelan Equine Encephalitis
LaCrosse Encephalitis Western Equine Encephalitis Japanese B Encephalitis
West Nile Encephalitis Powassan Encephalitis Dengue
Dengue hemorrhagic fever Chikungunya Congo-Crimean Hemorrhagic Fever
Colorado Tick Fever Russian Spring Fever Louping-ill
Barmah Forest Fever Mayaro Fever Murray Valley Encephalitis
Oropouche Fever Rift Valley Fever Sinbis Virus Disease
  Kyasanur Forest Disease