The viruses: WNV and CHIKV

West Nile virus (WNV)
WNV is a virus belonging to the family Flaviviridae, genus Flavivirus, and is spread by Culex pipiens mosquitoes. It can cause West Nile disease in human. This condition ranges from subclinical to mild and severe. Mild disease is manifested by fever, generally called West Nile fever. More severe forms of disease, which can be life threatening, are manifested by meningitis (inflammation of the protective membrane of the brain and spinal cord), encephalitis (acute inflammation of the brain), and flaccid paralysis (muscle weakness or paralysis). The most typical manifestations for WNV infections are neurological, and developement of WNV neuroinvasive disease is observed most frequently in the elderly and immuno-compromised individuals (individuals with a weakened immune system).

Chikungunya virus (CHIKV)
CHIKV is a virus of the genus Alphavirus, and is spread by Aedes mosquitoes. It is known to cause Chikungunya disease in humans, resulting in fever, and in severe cases in poly-arthralgia (multiple joint pain), meningitis, encephalitis, and flaccid paralysis. Although the most typical manifestations for CHIKV infections are rheumatic, an increasing incidence of neurological complications is reported during recent CHIKV infections as well. CHIKV neuro-invasive disease appears to represent the most common clinical manifestation among young children.