TEXT E The world’s last known case of smallpox was reported in Somalia, the Horn of Africa, in October 1977. The victim was a young cook called Ali Maow Maalin. His case becomes a landmark in medical history, for smallpox is the first communicable disease ever to be eradicated. The remarkable campaign to free the world of smallpox has been led by the World Health Organization. The Hom of Africa, embracing the Ogaden region of Ethiopia and Somalia, was one of the last few smallpox ridden areas of the world when the WHO-sponsored Smallpox Eradication Programme (SEP) got underway there in 1971. Many of the 25 million inhabitants, mostly farmers and nomads living in a wildness of desert, bush and mountains, already had smallpox. The problem of tracing the disease in such formidable country was exacerbated further by the continuous warfare in the area. The programme concentrated on an imaginative policy of "search and containment." Vaccination was used to reduce the widespread incidence of the disease, but the success of the campaign depended on the work of volunteers. These were men paid by the day, who walked hundreds of miles in search of "rumours"—information about possible smallpox cases. Often these rumours turned out to be cases of measles, chicken pox or syphilis-but nothing could be left to chance. As the campaign progressed the disease was gradually brought under control. By September 1976 the SEP made its first report that no new cases had been reported. But that first optimism was short-lived. A three-year-old girl called Amina Salat, from a dusty village in the Ogaden in the south-east of Ethiopia, had given smallpox to a young nomad visitor. Leaving the village the nomad had walked across the border into Somalia. There he infected 3,000 people, and among them had been the cook, Ali. It was a further 14 months before the elusive "target zero"—no further cases—was reached. Even now, the search continues in "high risk" areas and in parts of the country unchecked for some time. The flow of rumours has now diminished to a trickle--but each must still be checked by a qualified person. Victory is in sight, but two years must pass since the" last case" before an International Commission can declare that the world is entirely free from smallpox. The work to stamp out smallpox was made more difficult by______.

A. people’s unwillingness to report cases
B. the lack of vaccine
C. the backwardness of the region
D. the incessant local wars