West Nile Virus (WNV) is transmitted by mosquitoes. People who are infected with WNV may not experience any signs or symptoms. Some people experience minor symptoms like fever and mild headache. Others, however, can develop a life-threatening illness that includes inflammation of the brain.
People who experience mild signs and symptoms of a WNV infection generally recover on their own. But severe illness that includes a severe headache, disorientation or sudden weakness require immediate medical attention.