West Nile virus generally spreads to humans and animals from bites of infected mosquitoes. Mosquitoes get infected and carry the virus after biting infected birds. You can’t get infected from casual contact with an infected person or animal. Most West Nile virus infections happen during warm weather, when mosquitoes are active.
https://www.mayoclinic.org/diseases-conditions/west-nile-virus/symptoms-causes/syc-20350320

