The World Health Organization (WHO) released a statement on Monday stating that there is currently a high risk of polio spreading in Guinea and Mali after a Guinean toddler who travelled to Mali became the country's first case of the disease in more than four years, according to CBC News. The strain is allegedly vaccine-derived and the same as the one that was detected in Guinea's Kankan region back in August 2014.

"The risk of spread is considered to be high in both countries due to low rates of vaccination coverage in both Mali and Guinea," said WHO spokesman Cory Couillard. "Both countries are taking coordinated emergency response measures to bring the outbreak to an end quickly."

The strain surfaced when one of three live, weakened polio strains that were used in the vaccine mutated into a dangerous strain, according to The New York Times. Although mutations such as these are rare, many scientists warn that vaccine-derived fights against polio can lead to greater dangers. Vaccine-derived polio outbreaks are typically controlled by following them with several rounds of vaccinations in surrounding areas.

Despite research efforts, there is currently no cure for polio, which attacks the nervous system and can lead to permanent paralysis just hours after it spreads, according to Reuters.