POLIO IN WHO'S AFRICAN REGION, 2011

Thursday, 22nd of March 2012

POLIO IN WHO’S AFRO REGION, 2011

Full text, in English and French, is at http://www.who.int/wer/2012/wer8712.pdf

Editorial note

During 2011, polio eradication efforts in Africa have seen both progress and setbacks. While new outbreaks in 8 countries were interrupted—in 6 countries within 6 months of confirmation—WPV transmission persisted in Angola, Chad, DRC, and Nigeria. The number of WPV cases surged in Chad and Nigeria during 2011 compared with 2010.

The 2010–2012 GPEI Strategic Plan8 established the followingmilestones to track progress: (1) stopping WPVtransmission following importation in countries with outbreaks in 2009 by mid-2010; (2) stopping WPV transmission following importation in countries with outbreaks in subsequent years within <6 months after confirmation of the outbreak; (3) stopping WPV transmission in countries with re-established transmission by the end of 2010; (4) stopping WPV transmission in at least 2 of the 4 WPV-endemic countries by the end of 2011; and (5) stopping WPV transmission in all countries by the end of 2012.

Substantial obstacles to implemention of the 2010–2012 Strategic Plan in Africa have prevented achievement of important milestones. The first milestone was met for 14 of the 15 outbreaks occurring in 2009. However, transmission persisted during 2009–2011 in adjoining areas of Kenya and Uganda indicating substantial gaps in field surveillance quality; these gaps are being addressed.

Many areas in other countries of the Horn of Africa remain at risk of outbreaks following WPV importation, due to immunity and surveillance quality gaps. For example, civil conflict has prevented vaccination of around 1 million children aged <5 years in south-central Somalia for the past 18 months.

The second milestone was met or is on track for all outbreaks in 2010–2011, except for one outbreak in Mali and 2 in DRC that persisted for more than 6 months. New outbreaks following importation in 2011 were generally detected early and interrupted relatively rapidly as a result of immediate large-scale response immunization.By contrast, the large outbreak in the Republic of the Congo in 2010 was detected late and progressed because both detection and response immunization were delayed. The extensive outbreaks in West Africa due to WPV3 of Nigerian origin were also detected late, following prolonged undetected transmission. AFP surveillance systems in many countries of western, central and eastern Africa need urgent strengthening, particularly at the sub-national level, to improve the sensitivity of poliovirus surveillance in order to reliably exclude ongoing virus transmission and allow the rapid detection of and response to new outbreaks.

With re-established transmission continuing into 2011in Angola, Chad, and DRC, the GPEI failed to meet the third milestone. Persistent circulation in Angola caused outbreaks in Western DRC in 2011, from where northeastern Angola was re-infected. Seven years after WPV was first imported from India (2005), Angola now appears to be on-track to finally interrupt transmission.

However, to reliably document and maintain interruption of transmission, Angola also needs to strengthen surveillance and continue to conduct SIAs. In Chad, transmission of WPV3 of Nigerian origin was re-established from November 2007 to March 2011, followed by re-established transmission of WPV1 (also imported from Nigeria) since September 2010.

Prolongedre-established transmission in eastern DRC since 2006 and new outbreaks in western DRC are primarily due to chronic gaps in surveillance and low population immunity. An important additional risk factor in eastern DRC is refusal of vaccination amongparents from specific religious communities. In an effort to interrupt finally the transmission of re-established WPV in Chad and DRC, the number of national and international staff working on polio eradication was increased substantially in 2011 in both countries.

Regarding the fourth milestone of the 2010–2012 Strategic Plan, India has not detected a poliomyelitis case since mid-January 2011 and is no longer considered to be an endemic country. However, setbacks occurred in Afghanistan, Pakistan and Nigeria. Nigeria is the only country in Africa that has never eliminated transmission of indigenous WPV. The GPEI’s Independent Monitoring Board indicated that Nigeria and Pakistan pose the greatest risks to achieving the 2012 goal of interrupting the transmission of WPV globally.

Multiple polio outbreaks in previously polio-free African countries since 2003 have been traced to WPV imported from Nigeria. The goals of regional and global polio eradication will never be attained as long as WPV circulation continues in Nigeria. Operational problems in implementing high quality supplementary immunization activities (SIAs) continue to be the main reason why children remain unvaccinated in northern Nigeria.

New serious security challenges arose in Nigeria during 2011, further increasing the existing operational and managerial challenges to conducting SIAs with high coverage. In a concerted effort with GPEI partner agencies, the federal government of Nigeria is developing an emergency action plan aimed at restoring the programmatic momentum attained during 2009–2010.

Many innovative approaches to improve the microplanning and implementation of SIAs are being instituted. In May 2012, the World Health Assembly will consider a resolution declaring polio eradication an emergency for global public health. Urgent action is needed to improve the quality of SIAs implementation in the polio-affected countries of Nigeria, Chad and DRC. All other countries in Africa need to urgently improve the sensitivity of surveillance systems, and attain high levels of population immunity to reliably detect circulating or imported WPV and to prevent or limit the impact of new outbreaks.