scott cleland and gigi sohn, thank you very much. >> thank you. >> lehrer: finally tonight, a success story. it comes from southern sudan, where health workers have come close to eradicating a crippling disease called guinea worm. special correspondent fred de sam lazaro reports for our global health unit. a warning: you may find some of the images hard to watch. ( singing ) >> reporter: this remote corner of southern sudan is the homestretch of a campaign led by former president jimmy carter that could soon eradicate a scourge that dates back to biblical times. >> we will not stop the efforts of the carter center until there are no cases of guinea worm left in southern sudan or ghana or mali or ethiopia. that's the only places where we have a few cases left. >> we've been working on it now for more than 20 years. we've reduced it from more than two and a half million cases down to about 2,500 cases in the whole world and the last major holdout will be here in southern sudan. >> reporter: in southern sudan, ravaged by decades of civil war, fewer than half the people have access to cle