West Nile virus (WNV) is a virus that was first discovered in Africa and then spread to many regions of the world, including the Middle East, some countries in Europe and the former Soviet Union, as well as South Asia and Australia. The virus is transmitted by mosquito bites. It is also found during the warm months in North America, particularly in southern Quebec.
About 20% of people infected with West Nile virus present symptoms within two to 14 days of being bitten by a mosquito. Symptoms may vary and include headaches, fever, muscle aches, gastrointestinal disorders, skin rashes and swollen lymph nodes. In 1% of individuals, WNV infection can lead to serious neurological disorders such as meningitis or encephalitis. Symptoms that accompany this more severe form include severe headaches, high fever, stiff neck, nausea, vomiting, drowsiness, confusion and disorientation. Loss of consciousness and convulsions, as well as coordination disorders, muscle weakness and paralysis, are also possible. The severe form of WNV infection requires hospitalization and can cause permanent damage.
Antibodies produced by the body in response to WNV infection can be detected in a laboratory. Screening for IgM and IgG antibodies is usually based on a first sample collected as soon as possible after the onset of symptoms (acute phase), and then a second sample (convalescent serum) within seven to 14 days.