Phylogenetic analysis of wild-type 1 polioviruses isolated during the final period of transmission in Turkey.

The last poliomyelitis case associated with a wild poliovirus in Turkey occurred in November 1998. This was the last known case of paralytic poliomyelitis caused by indigenous wild poliovirus in the World Health Organization's European Region. This study investigated the genetic relationships of wild-type 1 polioviruses at the latest period of transmission. A phylogenetic tree was constructed on the basis of the VP1/2A sequence from 14 wild-type 1 polioviruses isolated from Turkey in 1994-1998, along with those from other areas of the world. The Turkey isolates in the latest period of transmission were closely related to each other, forming a cluster distinct from other strains. The results showed that these viruses had been spreading indigenously in the eastern and south-eastern parts of Turkey, and ceased transmission there during 1998. This finding serves as a reference for future poliovirus surveillance both in Turkey and worldwide.