JAKARTA, Indonesia - A strain of polio circulating in parts of Africa appears almost identical to one that has reached Indonesia, raising the prospect that a migrant worker may have brought it back to the Asian nation, the World Health Organization said Tuesday.

However, the U.N. health agency said it is confident the isolated import will not result in a major outbreak in Indonesia because the country's children are well protected by the polio vaccine and cases are quickly detected due to strong surveillance.

Two cases of polio have been confirmed in Indonesia, but authorities are confident they can prevent a major outbreak of the disease, Inndonesia's health ministry said.

The latest case was announced today. Dr. Umar Achmadi, head of communicable disease control for the ministry, told The Associated Press that the case was found in the same village in west Java where a 18-month old toddler contracted the disease last month.

"We did further investigation and we found six other cases of paralysis, we confirmed one more additional case, and five turned out negative," he said.

Achmadi said he was fairly certain that the second case - a 20-month old girl - came from the same source as the first, but that further tests were needed to confirm that.

Authorities say the strain is genetically similar to one in Nigeria, where the disease spread rapidly after Muslims boycotted the vaccine in 2003 amid rumors of a U.S.-led plot to render them infertile or infect them with AIDS.

The two cases are the first in Indonesia since 1995.

Since the boycott, the virus has broken across Nigeria's borders and six months ago sparked an outbreak in west and central African countries.

The genetic tests tracing the Indonesian case to Nigeria is somewhat of a relief, WHO says.

"It validates that it's an import and not a virus that has been lurking around Indonesia for 10 years and we haven't caught," said Sona Bari, a WHO spokeswoman for the polio eradication program.

"In that sense, it's a good thing, but what's not a good thing is seeing the results of the outbreak in 2003-2004 now heading out to Indonesia."

The case has prompted Indonesian health authorities to conduct house-to-house vaccinations in the area, intensify surveillance and draw up plans to vaccinate 5.2 million children under age 5 by July - the standard strategy for heading off outbreaks.

"We're pretty confident that we're going to get all the children at risk," Bari said from WHO's headquarters in Geneva, Switzerland.

Polio vaccination rates in Indonesia overall are about 90 percent. However, western Java, where the case occurred, is one of the low pockets, where only 55 percent of the children are protected by the vaccine, according to WHO figures.

Polio is a waterborne disease that usually infects young children, attacking the nervous system and causing paralysis, muscular atrophy, deformation and sometimes death.

Health officials are more worried about a recent cluster of cases in Yemen than about the cases in Indonesia, Bari added.

Only 69 percent of Yemen's children are vaccinated against polio and - located just across the Red Sea from Sudan - the country is close to the epicenter of the African outbreak.

Although Yemen had been polio-free since 1996, that proximity prompted authorities to launch a vaccine campaign last month to boost protection of its children.

However, less than a week after the first phase of the campaign was completed, four cases were confirmed in Yemen on April 20. Eighteen more cases have been confirmed in the last week, bringing the total there to 22. WHO expects more cases to emerge in the coming weeks.

The Yemen strain has been genetically traced to Nigeria.

Global eradication efforts have reduced the number of polio cases from 350,000 a year in 1988 to 1,267 cases last year.

The disease is still endemic in six countries: Nigeria, India, Pakistan, Niger, Afghanistan and Egypt. Transmission of the polio virus has been re-established in another six countries, sparking a regional epidemic in Ivory Coast, Chad, Central African Republic, Mali, Burkina Faso and Sudan.

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- Associated Press medical writer Emma Ross contributed to this story from London.