Tracking Progress Toward Global Polio Eradication --- Worldwide, 2009--2010

Tracking Progress Toward Global Polio Eradication --- Worldwide, 2009--2010
Weekly
April 15, 2011 / 60(14);441-445


Since the Global Polio Eradication Initiative (GPEI) began in 1988 (1), progress has been tracked by 1) surveillance comprised of detection and investigation of cases of acute flaccid paralysis (AFP), coupled with environmental surveillance (sewage testing) in selected areas, and 2) timely testing of fecal specimens in accredited laboratories to identify polioviruses. The sensitivity of AFP case detection and the timeliness of AFP investigations are monitored with performance indicators. Polioviruses are isolated and characterized by the Global Polio Laboratory Network (GPLN) (2). This report assesses the quality of polio surveillance and the timeliness of poliovirus isolation reporting and characterization worldwide during 2009--2010. During that period, 77% of countries affected by wild poliovirus (WPV) met national performance standards for AFP surveillance; underperforming subnational areas were identified in two of four countries with reestablished WPV transmission and in 13 of 22 countries with WPV outbreaks. Targets for timely GPLN reporting of poliovirus isolation results were met in five World Health Organization (WHO) regions in 2009 and in four of six regions in 2010; targets for timely poliovirus characterization were met in four WHO regions in 2009 and in five regions in 2010. Monitoring of surveillance performance indicators at subnational levels continues to be critical to identifying surveillance gaps that might allow WPV circulation to be missed in certain areas or subpopulations. To achieve polio eradication, efforts are needed to further strengthen AFP surveillance, implement targeted environmental surveillance, and ensure that GPLN quality is maintained.

AFP Surveillance

AFP surveillance, which detects paralytic illness of many causes, 1) identifies areas in countries with WPV circulation where polio cases might go undetected and supplementary immunization activities (SIAs)* are needed, 2) detects WPV circulation in previously polio-free areas, and 3) helps confirm the absence of WPV circulation in countries with only valid nonpolio AFP (NPAFP) test results. The quality of AFP surveillance is monitored with performance indicators for detection sensitivity and investigation timeliness established by WHO. Sensitivity is measured by the annual rate of AFP cases with adequate stool specimens testing negative for WPV among children aged <15 years (the NPAFP rate); investigation timeliness is measured by the proportion of AFP cases in which two adequate stool specimens were taken ≤14 days after onset and properly transported to an accredited GPLN laboratory (the specimen adequacy proportion).† Among the six WHO regions, the Region of the Americas was certified polio-free in 1998, the Western Pacific Region in 2000, and the European Region in 2002. During 2009--2010, Afghanistan, India, Nigeria, and Pakistan remained endemic with indigenous WPV transmission. WPV transmission in Angola, Chad, Democratic Republic of Congo (DRC), and Sudan, once polio-free countries, was reestablished after importation before 2009. During 2009--2010, the three WHO regions certified as polio-free maintained overall AFP surveillance sensitivity at ≥1 NPAFP case per 100,000 children, the WHO-specified national target, except for the European Region in 2009 (Table 1). In the three polio-endemic regions, an operational target of a national NPAFP rate of ≥2 cases per 100,000 children has been set for countries reporting WPV and for neighboring countries at risk for WPV transmission (3); this target was met in 27 (90%) of 30 polio-affected countries in both 2009 and 2010 (Table 1). Following WPV importation into the European Region in 2010, two outbreak-affected countries raised their NPAFP target rate to ≥2 from ≥1 in 2009. All WHO regions, except for the Americas in 2009, maintained an overall proportion of ≥80% AFP cases with adequate stool specimens, the WHO-specified national target (Table 1). The proportion of AFP cases with adequate stool specimens met the national target of ≥80% in 23 (77%) of the polio-affected countries in both 2009 and 2010 (Table 1). Surveillance quality varied substantially at subnational levels; 22 (73%) polio-affected countries achieved an NPAFP rate of ≥2 in ≥80% of subnational areas (states/provinces) in both years (Table 1, Figure). In only 18 (60%) countries was the standard of ≥80% of AFP cases having adequate specimens achieved in ≥80% of states/provinces in both years (Table 1, Figure). Analysis in relation to population distribution showed that only 15 (50%) of 30 polio-affected countries met both these standards in subnational areas: nine of 22 countries with outbreaks, all four countries with endemic WPV circulation, and two (Angola and Sudan) of the four countries with reestablished transmission. One concern is the clustering of states/provinces with suboptimal surveillance performance indicators within polio-affected countries or their neighbors and at country borders, such as Uganda/Kenya (Figure). Global Polio Laboratory Network full-text (large): Tracking Progress Toward Global Polio Eradication --- Worldwide, 2009--2010

Reported by
Polio Eradication Dept, World Health Organization, Geneva, Switzerland. Div of Viral Diseases; Global Immunization Div;* National Center for Immunization and Respiratory Diseases, CDC. *Corresponding contributor: IU Ogbuanu, MD, Global Immunization Div, National Center for Immunization and Respiratory Diseases (EIS Officer), CDC, 404-639-8757, ige2@cdc.gov.