Prior to the current outbreak, Syria’s last confirmed polio case (due to an imported wild poliovirus) was in 1999. Syria remained polio free until October 2013 when wild poliovirus was confirmed in Deir ez-Zor, and Aleppo, following importation of wild poliovirus closely related to strains currently circulating in Pakistan. The total number of confirmed polio cases in 2013 was 23.
