ST. PAUL, Minn. (AP) – Four children in a Minnesota Amish community have become infected with the polio virus, the first known infections in the U.S. in five years, state health officials said.

Health officials said the cases do not pose a threat to the general public because most people have been vaccinated against polio. But they said they expect to find more infections within the Amish community because some of its members refuse immunizations on religious grounds.

None of the children have shown any symptoms of the paralyzing disease. About one in 200 people who contract the polio virus suffer paralysis because of it; others typically shed the virus after weeks or months.

None of the four children had been vaccinated. Three are siblings; the fourth is an infant from another family.

Officials would not identify the Amish community but said it consisted of 100 to 200 people.

Dr. Harry Hull, the state epidemiologist, said the infections were traced back to an oral vaccine that was administered in another country, probably within the past three years.

Use of oral polio vaccine containing the live virus stopped in the United States in 2000. The live-virus vaccine caused an average of eight cases of polio a year in the United States. The U.S. and Canada now use an injected vaccine made from the killed virus.

State and federal officials are investigating how an infection from a vaccine given in another country reached Minnesota. Stool or saliva from an infected person can transmit the virus.

Health officials said they are working with the Amish community to determine who may have been exposed to the virus, and to encourage immunizations.

Hull said some parents in the community were allowing their children to be immunized but others were not. Because of that, he said, the virus could spread to other Amish communities.

The last naturally occurring case of polio in the United States was in 1979, and health officials consider the disease eliminated in the Western Hemisphere. It persists in other parts of the world, with the vast majority of cases concentrated in India, Nigeria and Pakistan, according to the World Health Organization.

According to the Centers for Disease Control and Prevention, more than 95 percent of U.S. children are vaccinated against polio by the time they enter school.

On the Net:

Minnesota Department of Health: http://www.health.state.mn.us/divs/idepc/diseases/polio/index.html

World Health Organization: http://www.polioeradication.org/disease.asp