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Wild poliovirus cases decreased in 2011 and 2012
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The number of countries with wild poliovirus and case numbers decreased during 2011 and 2012; however, efforts are still needed to improve and maintain acute flaccid paralysis surveillance and laboratory performance, according to data published in the Morbidity and Mortality Weekly Report.
In the 19 countries with transmission of poliovirus, national performance indicators were met in 12 of the countries in 2011 and 13 in 2012, CDC researchers said.
In 2011, 37% of the countries had at least 80% of the population living in areas meeting performance indicators, and this increased to 47% in 2012.
According to the CDC, all countries reporting poliovirus transmission in 2011 and 2012 met the target annual rate of at least two nonpolio acute flaccid paralysis cases per 100,000 people aged younger than 15 years.
Environmental surveillance also is being used in some countries to complement acute flaccid paralysis surveillance to determine where poliovirus circulates. Members of the Global Polio Eradication Initiative said they hope to expand use of environmental surveillance in high-risk areas for wild poliovirus transmission or circulative vaccine-derived poliovirus emergence.
CDC researchers said environmental surveillance is used in two currently polio-endemic countries (Nigeria and Pakistan) and 22 countries without active wild poliovirus transmission (India, Egypt and multiple sites in 20 countries of the WHO European region).
Wild poliovirus type 1 and vaccine-derived poliovirus were isolated from sewage samples from four sites in Sokoto, Nigeria, from March to December 2012. Vaccine-derived poliovirus type 2, wild poliovirus type 1 and wild poliovirus type 3 isolates were detected in Kano, Nigeria, from January to September 2012. Pakistan’s environmental sampling sites increased from 17 in 2011 to 23 in 2012, according to the researchers.
“Poliovirus transmission can be undetected in areas where gaps in acute flaccid paralysis surveillance quality exist, and this trend has been confirmed through laboratory analysis and environmental surveillance,” the researchers wrote. “Improving sensitivity for poliovirus detection will involve expanding environmental surveillance activities and strengthening acute flaccid paralysis performance, particularly at the subnational level, with ongoing supervision and monitoring of active surveillance at the health facility level.”
A new strategic plan will be submitted to the World Health Assembly in May to “reinvigorate the commitment of countries and other Global Polio Eradication Initiative partners toward polio eradication,” the researchers wrote. It will include specific efforts to interrupt transmission, certify eradication, withdraw oral polio vaccine and strengthen immunization and surveillance systems.
Disclosure: The researchers report no relevant financial disclosures.
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