Progress and peril: poliomyelitis eradication efforts in Pakistan, 1994-2013

Abstract

Pakistan is one of 3 countries where transmission of indigenous wild poliovirus (WPV) has never been interrupted. Numbers of confirmed polio cases have declined by >90% from preeradication levels, although outbreaks occurred during 2008-2013. During 2012 and 2013, 58 and 93 WPV cases, respectively, were reported, almost all of which were due to WPV type 1. Of the 151 WPV cases reported during 2012-2013, 123 (81%) occurred in the conflict-affected Federally Administered Tribal Areas (FATA) and in security-compromised Khyber Pakhtunkhwa province. WPV type 3 was isolated from only 3 persons with polio in a single district in 2012. During August 2012-December 2013, 62 circulating vaccine-derived poliovirus type 2 cases were detected, including 40 cases (65%) identified in the FATA during 2013. Approximately 350 000 children in certain districts of the FATA have not received polio vaccine during supplementary immunization activities (SIAs) conducted since mid-2012, because local authorities have banned polio vaccination. In other areas of Pakistan, SIAs have been compromised by attacks targeting polio workers, which started in mid-2012. Further efforts to reach children in conflict-affected and security-compromised areas will be necessary to prevent reintroduction of WPV into other areas of Pakistan and other parts of the world.

Keywords: Pakistan; disease eradication; epidemiology; polio; surveillance.

Figure 1.

Total cases of confirmed poliomyelitis and third-dose oral polio vaccine (OPV3) coverage—Pakistan, 1982–2013. Reported OPV3 coverage denotes the proportion of the target population who received OPV3, as reported by national authorities to the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF). Estimated OPV3 coverage denotes WHO-UNICEF estimates of the proportion of the target population who received OPV3. Non–polio-associated acute flaccid paralysis (NPAFP) case OPV3 coverage denotes the proportion of children who have NPAFP and received OPV3.

Figure 2.

Number of cases of wild poliovirus types 1 (WPV1), 3 (WPV3), and 1 and 3 (WPV1/WPV3), and circulating vaccine-derived poliovirus type 2 (cVDPV2), by month—Pakistan, 2010–2013. Abbreviations: bOPV, bivalent oral polio vaccine, types 1 and 3; mOPV, monovalent oral polio vaccine, type 1 or 3; NID, national immunization day; SNID, subnational immunization day; tOPV, trivalent oral polio vaccine.

Figure 3.

Cases of wild poliovirus types 1 (WPV1), 3 (WPV3), and 1 and 3 (WPV1/WPV3), and circulating vaccine-derived poliovirus type 2 (cVDPV2)—Pakistan, 2012–2013. Abbreviations: AJK, Azad Jammu and Kashmir; FATA, Federally Administered Tribal Areas. Data are current as of 4 February 2014. Each dot represents 1 poliovirus case. Dots are drawn at random within districts.

Figure 4.

Genetic profile of wild poliovirus cases in Afghanistan and Pakistan, 2012 (A) and 2013 (B). Maps were created on 30 April 2014. Each dot represents 1 poliovirus case. Dots are drawn at random within districts.