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When polio vaccination workers do visit their remote settlements, she says, they tend to visit only the first ruga they see and not look for others in the vicinity.

Once the liquid was in her mouth, they saw that it was held in ridges called rugae on the roof of the mouth before it continued down her throat.

On the summits of the rugae there are effusions of bloody matter, or spots of ecchymosis, presenting an appearance almost like crushed black currants.

The mucous membrane loses its rugae and presents a pale, grayish, blanched hue.

Finally, they spot a cluster of mud-brick huts, known to the Fulani nomads who live there as a ruga.