Polio--new challenges in 2006.

The continued progress of the Polio Eradication Program has encountered a number of hurdles in the past 2 years as virus has spread from northern Nigeria across much of central Africa and into the Middle East and as far as Indonesia. India continues to be a source of virus exportation but to a much less degree. WHO is optimistic regarding elimination of circulating virus from all of these countries in 2006 with the exception of Nigeria. Newly recognized obstacles to the eradication are the circulating vaccine-derived polioviruses (cVDPV) and those originating from immune deficient patients (iVDPV). Data are presented on the numbers and locations of cases of paralytic polio in 2004 and 2005 as reported to the WHO in early 2006. Scenarios for the maintenance of freedom from polio when/if the final cases occur are considered.