Last Friday, the WHO IHR Emergency Committee convened and issued a statement that the global spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC). It cited concerns that removal of the PHEIC and accompanying recommendations would “[contribute to] a risk of global complacency” towards eradication efforts. The PHEIC has been in effect since May 2014. To-date, WHO has labeled only four disease emergencies as PHEICs.

In its decision to extend the PHEIC, the IHR Emergency Committee cited setbacks in Afghanistan’s polio eradication program, “stagnation” of efforts in Pakistan, and the spread of circulating vaccine-derived poliovirus (cVDPV) in multiple countries in central and east Africa. However, the committee noted some positive developments in the global effort to eradicate polio, including an end to circulating vaccine-derived poliovirus type 2 in Syria. In light of the Emergency Committee’s decision, we provide an update on the progress made by the global effort to eradicate polio in 2018.

Continued occurrence of vaccine-derived and wild poliovirus

In June 2017, Outbreak Observatory reported on the confirmation of cVDPV cases in Syria and the Democratic Republic of the Congo (DRC). Despite the name, the occurrence of cVDPV cases does not signal a problem with the vaccine being used. Rather, vaccine-derived polioviruses can occur in populations that are susceptible to infection due to low immunization coverage. Thus, the occurrence of cVDPV cases in Syria and DRC countries signified a lack of progress in polio eradication efforts, in part due to challenged public health systems and ongoing political instability in both countries.

In a sign of progress this week, an assessment panel comprising global health experts concluded that the outbreak of cVDPV in Syria has officially ended. cVDPV type 2 was discovered in eastern Syria in June 2017 and resulted in 74 cases, but no additional cases have been reported since September 2017. WHO officials attributed the containment to improved access for both surveillance and vaccination activities. Wild poliovirus (WPV) returned to Syria in 2013—18 years after it was declared eliminated from the country—due to the public health consequences of the Syrian civil war.

In contrast, DRC remains affected by three separate strains of cVDPV type 2 in central and eastern regions of the country. The country has reported 19 cases of cVDPV type 2 so far in 2018, compared to 22 cases in 2017. Of concern, one of these outbreaks is occurring alongside an outbreak of Ebola virus disease in the country’s east, including in Ituri province, which confirmed cases of both diseases this year. According to GPEI, the concurrence of Ebola has required close coordination of polio teams with the broader humanitarian emergency network. Other African countries that confirmed samples of cVDPV in 2018 include Niger, Nigeria, Kenya, and Somalia.

Afghanistan and Pakistan have historically ranked among the most challenging contexts for polio eradication. While Pakistan has witnessed a significant reduction in WPV cases in recent years—with 8 confirmed cases in 2018 down from 306 cases in 2014—WPV cases in Afghanistan have increased to from 14 last year to 19 this year.

One country, Nigeria, has had to guard against circulation of endemic WPV as it simultaneously confirmed multiple outbreaks of cVDPV type 2 in the country’s remote northern states. Nigeria has not reported a case of WPV in more than two years, since August 2016; however, ongoing endemicity of WPV cannot be ruled out. Meanwhile, it has had to battle separate outbreaks of cVDPV totaling 31 cases. The outbreaks originated in Jigawa state (with subsequent spread to neighboring states, as well as the country of Niger) and Sokoto state.

Progress towards eradication

To assess progress towards eradication and make recommendations for strengthening the response, GPEI’s Independent Monitoring Board (IMB) commissioned a team, including Outbreak Observatory advisor, Athalia Christie, to travel to the 3 remaining endemic countries of Pakistan, Afghanistan, and Nigeria.  The IMB report, issued in September, provides a comprehensive look at the successes and constraints of the country-level response.

Among the conclusions, the IMB found that the situation in Pakistan has “improved dramatically” since 2014. Some of the gains can be attributed to efforts by the Pakistani police and military, which have been “instrumental in improving access” of frontline health workers to remote populations and reducing incidents of violence perpetrated by the Pakistan Taliban. A community-based vaccination program, which recruits local female workers to conduct vaccinations, has also been successful in improving access to previously inaccessible populations.

However, the IMB report cautioned against complacency in Pakistan. They noted that polio incidence has not decreased since 2017, with the same number of cases (8) so far reported in 2018. The report noted there is widespread environmental circulation of WPV based on positive specimen testing, a large number of children whose families refuse vaccination due to misconceptions about the polio vaccine, and a new government in Pakistan whose commitment to eradicating polio is strong but remains untested. Overall, Pakistan “has the potential to interrupt transmission,” according to the report, but further efforts are needed to strengthen immunity domestically.

Conversely, Afghanistan “represents the most significant impediment to global eradication efforts.” The IMB research team found that a deteriorating security situation is hampering immunization activities, resulting in more than a million children missing vaccination in the months of May and August. Access to the country’s Eastern Region has become severely restricted, including violent threats against polio workers and intensive propaganda against the eradication effort. The report also raised questions over the leadership and structure of Afghanistan’s polio eradication program.

Finally, in Nigeria, the IMB research team found that “after two years without a case, there are grounds for optimism that Nigeria is succeeding, but there is no room for complacency.” Specifically, the humanitarian conflict in the country’s northeast states, including Borno, home to the Boko Haram militant group, has limited the accessibility of these areas to polio workers. According to the report, satellite images estimate that 100,000 children under 5 remain trapped in areas controlled by Boko Haram. Internally displaced people who have fled Boko Haram, and now reside in refugee camps, are comparatively easier for polio workers to vaccinate and monitor.

Similarly, a report published this week by the International Peace Institute on “Providing Healthcare in Armed Conflict,” which involved travel to Nigeria, reported that Nigeria’s government prohibits humanitarian actors from traveling to Boko Haram-controlled areas of Borno state. Nevertheless, the polio immunization campaign is unique in that it is allowed to enter restricted areas by receiving escorts from the Nigerian military or local anti-Boko Haram militia, known as the Civilian Joint Task Force. The IMB report acknowledges that while this allows vaccination opportunities, it warns that coordinating with the military and the Civilian Joint Task Force “requires careful consideration,” as these groups have been accused of human rights violations and may blur the lines between humanitarian and military activities in the region.


Progress towards polio eradication in 2018 has been mixed. Gains can be found in some settings, including Syria, where cVDPV type 2 was officially declared over; however, this is not consistent across the remaining problem areas. Pakistan continues to report record low numbers of WPV cases, although it did not improve upon last year’s case counts. The challenging security and operational environment that makes Afghanistan one of the world’s last refuges for WPV appears to be worsening.

A common theme to emerge from polio eradication efforts in Afghanistan, Pakistan, Syria, DRC, and Nigeria is that the security and humanitarian situation is closely linked to the ability of polio workers to access remote populations and effectively implement eradication activities. As Sania Nishtar writes, these regions are often the most vulnerable and subject to weaknesses in broader health services delivery. Restrictions by armed groups or mistrustful local communities (a trend also observed in DRC’s recent Ebola outbreak) can further result in reduced immunization rates, gaps in surveillance, and other programmatic failures.

It is perhaps little surprise that the WHO IHR Emergency Committee cited inaccessibility as a “major risk” for the spread of poliovirus, and one of its justifications for maintaining the PHEIC declaration. Similarly, as noted in the IMB report, focusing on improving surveillance and vaccination in inaccessible areas should remain “a top priority” if the GPEI is to be successful.

Photo: Community members and public health practitioners in Mozambique update a map of their village to ensure all children are reached during a 2017 polio vaccination campaign; courtesy of CDC/Nancy Andrade.

Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly to allow others to learn from these experiences in order to improve global outbreak response capabilities.