WASHINGTON - Polio has spread out of Nigeria to reinfect neighboring countries that had eliminated the disease, the US Centers for Disease Control and Prevention reported yesterday.

The new Nigerian outbreaks set back a bid to wipe out the water-borne disease globally, the CDC said in its weekly report on death and disease. Polio attacks the nervous system and can cause paralysis, breathing problems, and sometimes death.

"Despite accelerated efforts, polio cases increased 26 percent, from 1,315 cases in 2007 to 1,655 in 2008.

This increase primarily resulted from an increase in Nigeria from 285 cases in 2007 to 801 cases in 2008," the CDC report said.

"During the second half of 2008, (polio) originating from northern Nigeria spread to eight neighboring African countries, including six that had been polio-free since having cases during 2003-2005."

The World Health Organization and several private groups, including Rotary International and the non-profit Bill & Melinda Gates Foundation, have been working to eradicate polio through a global vaccination effort.

It has been successful except in a few areas, mostly those experiencing conflicts, that have provided a hiding place and breeding ground for the virus.

Wild polio - as opposed to a rare infection caused by one of the vaccines - has been wiped out everywhere but in four countries: Afghanistan, India, Nigeria, and Pakistan.

Nigeria reported 801 polio cases in 2008, but the virus has also spread into Angola, Chad, the Democratic Republic of Congo, Niger, and southern Sudan, the CDC said.

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