-- The South African government plans to immunize all children in the country younger than 5 against polio, officials said Wednesday, as global eradication efforts struggle against outbreaks on a continent where the disease had largely been eliminated.

Nine African countries that had been free of polio have reported cases in the past two years. Eradication in South Africa has gained new urgency after a case was reported in neighboring Botswana in February.

South African health officials say they hope to reach all 5 million children younger than 5 with two rounds of the vaccine from July through September. The nearly $4 million program would be the country's fifth mass vaccination campaign since the establishment of multiracial democracy in 1994.

"Practically everyone's welfare is tied up in this, so we're targeting every child," said Joanne Collinge, a spokeswoman for the Health Ministry, adding that previous efforts have reached more than 90 percent of South African children.

Polio is considered endemic, or freely circulating, in six countries: Nigeria, Niger, Egypt, India, Pakistan and Afghanistan. Officials say that if the disease is not conquered soon, it could spread rapidly to other countries.

"We're at a critical junction," said Melissa Corkum, a World Health Organization spokeswoman. "While polio is circulating anywhere, children are at risk everywhere."

Recent setbacks have cast doubt on efforts to eradicate polio around the world this year. Several predominantly Muslim states in northern Nigeria temporarily suspended vaccinations last year because of rumors they were part of a plot to cause sterility among Muslims. One state, Kano, has not resumed its program.

Nigeria is home to 170 of the 236 cases of polio reported worldwide this year, according to the Global Polio Eradication Initiative, a partnership of several health organizations.

Bruce Aylward, coordinator of the Global Polio Eradication Initiative, said the resurgence of the disease is rapidly threatening to undo years of progress, especially in Africa.

"We could really see the largest outbreak of polio in recent history," Aylward said, "so the stakes are high."

The case in Botswana alarmed public health officials because the country had been free of polio since 1991. Tests indicated that the case was genetically similar to the variant of the disease found in Nigeria, thousands of miles to the northwest.

The victim, a 7-year-old boy, has recovered and regained full use of his legs, said Patson Mazonde, a health official in Botswana.

Botswana began a mass vaccination program in May that officials said reached nearly all of the country's 222,000 children younger than 5. This week, health workers are attempting to visit every household in the country to administer a second round, which is necessary to provide full immunity.

"We are moving from house to house," Mazonde said. "Even the most remote areas, we have dispatched teams to these areas."

About 63 million children in 10 countries in West and Central Africa have been immunized this year. Several other African countries are also planning mass vaccination campaigns, officials said.