There is a high risk of polio spreading in Ebola-ravaged Guinea and Mali, the World Health Organization said on Monday, after a Guinean toddler traveled to Mali and became that country's first case of the crippling disease in more than four years.

"The risk of spread is considered to be high in both countries due to low rates of vaccination coverage in both Mali and Guinea," WHO spokesman Cory Couillard said in an emailed comment to Reuters.