UN agencies and Sudanese health officials began a two-day countrywide polio immunisation campaign on 23 October, following reports of a new case of the disease in Darfur.

No polio cases had been reported in Sudan since August 2005, granting the country WHO certification as polio-free. The new case, which was confirmed in a boy from South Darfur, may have spread from neighbouring Chad, the health agency said.

"Sudan will implement coordinated and cross-border outbreak response activities as Chad synchronises its response in the next two months," Mohamed Abdurrab, WHO representative in Sudan said.

Some villages in Darfur could not reached by vaccinators during a three-day campaign in August due to insecurity in the war-torn region. That campaign also followed reports of polio in Chad.

Officials said more vaccinations would be administered in November.

A highly infectious viral disease, polio invades the nervous system and can cause total paralysis in a matter of hours.