In its ongoing series examining efforts to eradicate polio, NPR health editor Joe Neel and Jason Beaubien, a global health and development correspondent for the news service, on Thursday spoke with “Talk of the Nation” host Neil Conan about obstacles to stamping out polio in the three countries where the disease persists — Afghanistan, Pakistan, and Nigeria. According to the transcript, they discuss how “[o]bstacles in each country, including religious extremism, difficult terrain and transient populations, make eradication efforts difficult” (10/25).