West Nile virus is a viral disease that is transmitted by mosquitoes. The virus is a member of the Flaviviruses, which also includes Zika, dengue and yellow fever viruses. The virus was first identified in the West Nile district of Uganda in 1937,

Philadelphia health officials are warning residents after West Nile virus was found in mosquitoes in Northeast Philadelphia earlier this month.

City health officials instructed Philadelphia medical providers to check patients for West Nile virus and other mosquito-borne illnesses and immediately report cases.