Paralytic poliomyelitis outbreak in Gizan, Saudi Arabia.

An outbreak of paralytic poliomyelitis occurred in the Southern region of Saudi Arabia between April and August of 1989. Poliovirus type 1 (wild type) was isolated from the stool of 4 out of 11 patients and 10 out of the 11 patients had a high neutralizing antibody to the isolated virus (greater than or equal to 256). The results were confirmed by the Centers for Disease Control (CDC), Atlanta. The fact that the outbreak occurred despite a high level of immunization coverage and that all our cases had already been immunized with sabin oral polio vaccine (OPV) is probably an indication of the unsatisfactory performance of OPV in tropical and subtropical countries. Other implication of this outbreak are also discussed.