LONDON (AP) — The World Health Organization says Zambia has reported its first local case of polio since 1995, in a 2-year-old boy paralyzed by a virus derived from the vaccine.

In a report this week, WHO said the case was detected on the border with Congo, which has reported 37 cases of polio traced to the vaccine this year. The U.N. health agency said there is no established link between the Zambia case and the Congo outbreak but increased efforts are needed to prevent international spread.

In rare cases, the live virus in oral polio vaccine can mutate into a form capable of sparking new outbreaks.

Nine African countries are currently battling polio epidemics linked to the vaccine as WHO and partners struggle to keep their efforts to eradicate polio on track.