Molecular epidemiology of poliovirus infection in Tunisia

This report is an overview of poliomyelitis surveillance in Tunisia from 19 91 to 1996, In all, 2088 stool specimens, collected from 152 acute flaccid paralysis (AFP) cases and from 1747 of their healthy contacts were investig ated. Virus isolation was done systematically in RD and HEp-2C cell lines a nd isolated viruses were typed by seroneutralisation as polioviruses or non -polio enteroviruses, Poliovirus isolates were analysed systematically for their wild or vaccine-related origin by two methods - one based on antigeni c differences and one on genetic differences between strains. All type 2 po lioviruses were vaccine-related and most wild viruses belonged to polio ser otype 3, Wild polio type 3 viruses were detected in 1991 and 1992 in six ca ses of paralytic polio. A silent circulation of wild polio 1 and wild polio 3 was detected in 1994, No wild virus was detected in Tunisia from 1995 on wards. Wild polioviruses were sequenced and compared with Tunisian wild str ains isolated during the 1980s, as well as other genotypes from the interna tional database. These investigations revealed a single Tunisian polio 3 ge notype that has been circulating from 1985 to 1994 and two different polio 1 genotypes, These results reflect effective control strategies nithin the country and contribute to the improvement of the polio eradication programm e effectiveness at national and global levels.