ISLAMABAD (AP) — Pakistan detected one more polio case in the restive northwest bordering Afghanistan, raising the country's tally of the infectious disease to 50 cases this year, officials said Wednesday. Pakistan and Afghanistan are the only two countries in the world where the spread of polio has never been stopped. The sudden rise in cases of polio, which is an infection caused by a virus that mostly affects children under 5, has hampered the country's yearslong efforts to make it a polio-free state.