Zimbabwe starts an emergency polio vaccination drive after detecting cases caused by a rare mutation

Zimbabwe has started an emergency campaign to inoculate more than 4 million children against polio after health authorities detected three cases caused by a rare mutation of the weakened virus used in oral vaccines. The health ministry said laboratory tests from samples collected from sewage sites in several areas in the capital late last year showed the presence of a mutated polio virus. In rare instances, the live polio virus in vaccines can mutate into a form capable of sparking new outbreaks, especially in places with poor sanitation and low vaccination levels.