Uptick in Worldwide Polio Cases in 2013 Continues Into 2014

Janis C. Kelly

June 02, 2014

The World Health Organization (WHO) campaign to eradicate polio reduced incidence rates by more than 99% between 1988 and 2013, but between 2013 and 2014, investigators saw an 86% increase in wild polio virus (WPV) cases worldwide, researchers report in an article published in the May 30 issue of the Morbidity and Mortality Weekly Report.

In 2012, there were 223 cases in 5 countries, and in 2013, the number rose to 416 cases in 8 countries.

"This upsurge in 2013 was caused by a 60% increase in WPV cases detected in Pakistan, and by outbreaks in five previously polio-free countries resulting from international spread of WPV. In 2014, as of May 20, a total of 82 WPV cases had been reported worldwide, compared with 34 cases during the same period in 2013," Edna K. Moturi, MBChB, an Epidemic Intelligence Service Officer at the CDC, and colleagues authors note. They add that improving this situation will require addressing the safety concerns of health workers "in areas of armed conflict in priority countries," preventing WPV spread back into currently polio-free countries, and strengthening global polio surveillance.

The global polio vaccination initiative achieved between 84% and 97% coverage of infants by age 12 months in most of the word during 2012. However, coverage was notably lower in the countries in which polio is endemic, which are seeding the upsurge in new cases: Nigeria (59% vaccination rate), Afghanistan (71%), and Pakistan (75%). Countries in Africa and the Eastern Mediterranean Region were targeted for supplementary immunization activities (SIAs) in 2013, and more SIAs are planned, the report said.

Of the new WPV cases reported in 2013, 22% were in Pakistan and 62% were new outbreaks in previously polio-free countries after the importation of WPV1. During the January to April "low transmission season," 82 cases were reported from 8 countries in 2014 compared with 34 cases from 3 countries in 2013.

"During 2014, as of May 20, WPV1 has already spread internationally from three countries: in central Asia (from Pakistan to Afghanistan), the Middle East (Syria to Iraq), and in Central Africa (Cameroon to Equatorial Guinea)," the authors write.

Nigeria reported a 57% decrease in the number of cases and a 50% reduction in the number of districts with new polio cases from 2012 to 2013. The declines continued into the first part of 2014, with just 3 new cases compared with 16 in the same period in 2013, which is an 88% decline. This improvement came despite suspension of SIAs because of armed conflict in northeastern Nigeria.

Similarly, Afghanistan reported just 14 cases in 2013 from 10 districts, compared with 37 cases in 2012 from 21 districts, which represents a 62% drop in cases and a 52% decline in districts affected. In the first part of 2014, authorities reported 4 cases compared with just 2 during the same part of 2013.

"The continued ban on polio vaccination in North and South Waziristan, Federally Administered Tribal Areas where local leaders have prevented vaccination of >350,000 children since June 2012, is largely responsible for the increase in WPV cases in 2013 and 2014 in Pakistan and for recent WPV importation into Afghanistan and war-torn Syria," the authors write.

Outbreaks in previously polio-free countries increased from 6 cases in 2 countries (Chad and Niger) in 2012 to 256 cases in 5 countries in 2013. WPV imported from Nigeria caused polio cases in Ethiopia, Kenya, and Somalia. Polio imported from Pakistan caused 35 cases in Syria in 2013 and 1 case in 2014. Polio imported from Syria caused 1 case in Iraq.

The good news is that 80% of the world's population now lives in polio-free regions, and indigenous WPV transmission within the 2 remaining regions with endemic polio (Africa and the Eastern Mediterranean) was restricted to fewer areas within each of the 3 countries in which polio remains endemic. The authors predict that interruption of global polio transmission could be achieved in the near future if outbreaks after importation into polio-free countries can be prevented or treated promptly, which will require "enhanced commitment by countries" and coordinated efforts to maintain current gains.

On May 5, 2014, the Director General of the WHO declared the recent international spread of WPV a public health emergency of international concern and introduced several temporary recommendations to reduce further spread of the virus. The WHO recommendations included requiring vaccination of residents and long-term visitors traveling from Cameroon, Pakistan, and Syria before international travel; encouraging vaccination of residents and long-term visitors traveling from Afghanistan, Equatorial Guinea, Ethiopia, Iraq, Israel, Somalia, and Nigeria to receive vaccination before international travel; and having providing an International Certificate of Vaccination documenting the vaccination status for all such travelers.

The authors have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. 2014;63:468-472. Full text

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