The World Health Organization (WHO) says two cases of polio have been reported in Ukraine, the first such outbreak of the disease in Europe since 2010.
In a statement on September 2, WHO said two children in southwestern Ukraine had been paralyzed by polio.
WHO said the outbreak occurred because only half of Ukrainian children are immunized against the disease.
WHO warned that the risk of further spread of polio in the country is high.
WHO said the risk for nearby countries -- Romania, Poland, Hungary and Slovakia -- is low.