U.S. added to WHO's list of countries with circulating polio

The World Health Organization added the U.S. to the list of countries where vaccine-derived poliovirus is circulating according to a CDC announcement.

Why it matters: The U.S. joins a list of about 30 other countries, including Israel and the U.K., where circulating vaccine-derived polioviruses have been identified, the CDC said.

Be smart: Vaccine-derived poliovirus spreads from a person who takes the oral polio vaccine, which is no longer used in the U.S. but is in other parts of the world, who then sheds some of that weakened virus from the vaccine.

• Among the unvaccinated, it can be spread through means including person-to-person contact or droplets from a sneeze or cough, per the CDC.

"We cannot emphasize enough that polio is a dangerous disease for which there is no cure," José Romero, CDC director at the National Center for Immunization and Respiratory Diseases, said in a news release.