OUTBREAK OF POLIOMYELITIS IN GIZAN, SAUDI-ARABIA - COCIRCULATION OF WILD-TYPE-1 POLIOVIRUSES FROM 3 SEPARATE ORIGINS

In 1989, a localized outbreak of 10 cases of poliomyelitis occurred in Saudi Arabia. Wild poliovirus type 1 was isolated from 5 patients. To determine the patterns of poliovirus circulation, partial nucleotide sequences of the poliovirus isolates were compared. These isolates wer e remarkably diverse. Two isolates were closely related to each other and to viruses isolated during the 1988 epidemic in Oman. Two other is olates were very similar to viruses found in Egypt, The fifth isolate was distantly related to the latter pair. The molecular data suggest t hat the 10 cases represented three separate outbreaks. The virologic f indings underscore the potential for Saudi Arabia, which receives mill ions of guest workers and their families each year from countries in w hich polio is endemic, to be exposed to frequent importations of wild polioviruses. To restrict the circulation of imported polioviruses, Sa udi Arabia must maintain high population immunity to poliovirus in all geopolitical divisions.