In this Feb. 9, 2014 photo, a Pakistani health worker vaccinates a child against polio, in Peshawar, Pakistan. Pakistan’s beleaguered battle to eradicate polio is threatening a global, multi-billion dollar campaign to wipe out the disease worldwide. Because of Pakistan, the virus is spreading to countries that were previously polio free, say U.N officials. “The largest poliovirus reservoir of the world,” is in Peshawar, the capital of Pakistan’s northwest Khyber Pukhtunkhwa province, which borders Afghanistan, according to the World Health Organization. (AP Photo/Mohammad Sajjad)