Resurgence of wild poliovirus type 1 transmission and consequences of importation–21 countries, 2002-2005

After the 1988 World Health Assembly resolution to eradicate poliomyelitis globally, the number of polio-endemic countries decreased from 125 in 1988 to six (Afghanistan, Egypt, India, Niger, Nigeria, and Pakistan) in 2003. However, during 2002-2005, a total of 21 previously polio-free countries were affected by importations of wild poliovirus (WPV) type 1 from the six remaining countries (primarily Nigeria) where WPV was endemic; four countries (Indonesia, Somalia, Sudan, and Yemen) had outbreaks of >100 polio cases. By the end of 2005, WPV transmission in all 21 countries except Somalia had been interrupted or substantially curtailed. This report summarizes WPV importations into polio-free countries during 2002-2005 and the status of WPV transmission in these countries as of January 24, 2006, and describes actions that polio-free countries can take to improve importation preparedness.