Polio Surge
Abstract
Sparked by concerns about a surge of poliomyelitis cases in Nigeria caused by a vaccine-derived strain of type 2 poliovirus, health officials stepped up efforts to curb its spread, according to the Global Polio Vaccine Initiative (http://www.polioeradication.org/content/general/current_monthly_sitrep.asp). Although type 2 wild poliovirus (1 of the 3 serotypes of wild poliovirus) had been eradicated in 1999, it reemerged a few years ago when weakened type 2 virus in oral polio vaccine mutated....