The World Health Organization confirmed two cases of wild poliovirus type 1 in Cameroon on Thursday, marking the first human cases there since 2009.

The virus was isolated from two patients in the country’s western region who had developed paralysis in October; genetic sequencing indicated the cases are linked to the strain detected in neighboring Chad in 2011. The W.H.O. said an emergency plan to tackle the outbreak, including at least three national immunization days, was being finalized and that a response would also be implemented for Chad and the war-torn Central African Republic.

Earlier this year, Cameroon reported four cases where people in the Far North region had developed paralysis due to circulating vaccine-derived poliovirus type 2, linked to Chad and detected in Nigeria and Niger.

Cameroon is considered at high risk for reinfection due to its long shared border with Nigeria, one of three countries where the virus remains endemic, along with Afghanistan and Pakistan. On Nov. 19, UNICEF announced that Afghanistan’s southern region hadn’t reported a new case of polio in a full year, but that efforts would be focused on the eastern region along the tense border with Pakistan. Of 334 worldwide cases reported so far in 2013, only nine have been in eastern Afghanistan; that figure is one-third of last year’s total.

The virus’ reemergence in Cameroon comes weeks after W.H.O. officials confirmed the debilitating disease had returned to Syria, which had been declared polio-free in 1999.

That strain, confirmed to have originated in Pakistan, has crippled at least a dozen children from 22 suspected cases in Deir al-Zor province. Global public health officials are concerned that Syria’s civil war, especially with the entry of foreign fighters and mass movement of refugees around the region, is pushing the disease further away from eradication.