Statement of the Seventeenth IHR Emergency Committee Regarding the International Spread of Poliovirus

from World Health Organization
Published on 10 May 2018 View Original

10 May 2018

The seventeenth meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) regarding the international spread of poliovirus was convened by the Director General on 30 April 2018 at WHO headquarters with members, advisers and invited member states attending via teleconference.

The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polioviruses (cVDPVs). The Secretariat presented a report of progress for affected IHR States Parties subject to Temporary Recommendations. The following IHR States Parties provided an update on the current situation and the implementation of the WHO Temporary Recommendations since the Committee last met on 7 February 2018: Afghanistan, Democratic Republic of Congo (DR Congo), Pakistan, Kenya, Somalia and Syrian Arab Republic.

Wild polio

Overall the Committee was encouraged by continued progress in WPV1 eradication, with the number of cases globally remaining low in 2018. In addition, there has now been no international spread of WPV1 since October 2017.

The Committee commended the continued high level commitment seen in both Afghanistan and Pakistan, and the high degree of cooperation and coordination, particularly targeting the high risk mobile populations that frequently cross the international border. The joint planning to cease transmission in the two recognized zones of transmission (the northern corridor which extends from Nangarhar to Islamabad and Rawalpindi, and the southern corridor from Kandahar to Quetta Block) is a key to success in achieving WPV eradication in Pakistan and Afghanistan, the region, and globally.

The Committee commended the achievements in Pakistan that have resulted in a sustained reduction in the number of cases, with only one case so far in 2018, and a fall in the proportion of environmental samples that have tested positive for WPV1. No orphan virus (viruses that are not closely related to any other virus based on genetic analysis) has been detected so far in 2018, giving some confidence that surveillance is working well. Notable achievements include better quality supplementary immunization activities (SIA) and improved communication to reduce missed children. However, environmental surveillance continues to detect WPV1 transmission in many high risk areas of the country such as Karachi, Peshawar and the Quetta Block. The robust response to environmental detections of WPV was welcomed.

The Committee was concerned by the stagnation in progress in Afghanistan and the ongoing risks to eradication posed by the number of inaccessible and missed children, particularly in the southern and eastern regions, resulting in fourteen cases in 2017, and already seven cases in 2018. The continued inaccessibility in Kandahar, Paktika, and parts of Nangarhar and Kunar, and issues with vaccine acceptance in some high risk areas particularly in Kandahar, the Bermel district of Paktika, and Kunar are the biggest challenges. Of greatest concern are the children chronically unreached by the polio program, these numbering around 13,000 children in Shahwalikot and 40,000 children living in areas controlled by militant anti- government elements in the eastern region.

The Committee commended the innovations that continue to be made in Nigeria to reach children in Borno, where the number of inaccessible children has fallen from 160,000 in late 2017 to around 104,000 currently. While certain cross border activities are being undertaken, such as international synchronization of vaccination campaigns, these efforts appeared to be insufficient to ensure that any poliovirus still circulating undetected is not exported to neighboring Lake Chad basin countries. The Committee also noted that routine immunization coverage is low, particularly in high risk areas of northern Nigeria. The country however has declared routine immunization a national public health emergency and is actively planning for Gavi transition with strengthening of its routine immunization program in mind. Although it is over 19 months since the last detection of WPV1 in Nigeria, the outbreak response assessment by global polio experts concluded ongoing undetected transmission could not be ruled out.

There is ongoing concern about the districts of the neighboring countries of the Lake Chad basin region that have been affected by the Boko Haram insurgency, with the consequent lack of services and presence of IDPs and refugees. The risk of international spread from Nigeria to the Lake Chad basin countries or further afield in sub-Saharan Africa remains substantial. The Committee was encouraged that the Lake Chad basin countries, Cameroon, Chad, the Central African Republic (CAR), Niger and Nigeria continued to be committed to sub-regional coordination of immunization and surveillance activities. However, there are widespread persistent gaps in population immunity across these countries, and the ongoing population movement in the sub-region and insecurity are major challenges. The committee urged that work to characterize and vaccinate transient and permanent populations on the Lake Chad islands continue urgently.

Vaccine derived poliovirus

The committee noted that in DR Congo, the vaccine-derived polio outbreak has now been declared a public health emergency, with resources being made available for an emergency operation centre, appointment of a national outbreak coordinator, and other resources. However, there has been further transmission into new areas not covered by previous mOPV2 campaigns, with the report of a case in Haut Katanga province, and another eight cases reported in previously affected provinces. Further rounds with mOPV2 are being planned. Risks are compounded by poor surveillance in many areas, and widespread gaps in population immunity. It was noted that upcoming elections with the possibility of civil unrest posed an additional risk to the ability of the country to halt the outbreak. The movement of refugees and IDPs increases the risk of further spread, and the IPV shortage in neighboring countries is another risk, with the under 2 age group vulnerable to type 2 infection. In DR Congo, insecurity and geographical remoteness of the affected area pose significant challenges to controlling the outbreak.

The committee noted that in Syria, there has been no new case for more than six months, giving hope that transmission may have stopped. However, while AFP surveillance indicators are good, and environmental surveillance is now in operation, low level transmission cannot yet be ruled out.

The new outbreak of cVDPV2 with international spread affecting Somalia and Kenya is a major concern, together with the recent detection of cVDPV3 by environmental sampling in Mogadishu. While the robust response to date was commendable, the lack of clarity about where the virus emerged and circulated for a prolonged period prior to detection means that it remains unsure whether the population currently being targeted is sufficient. The persistently inaccessible districts in the South and Central zones of Somalia makes an effective response extremely difficult, with more than 300,000 children aged under 5 years believed to be living in these districts. Nomadic and refugee movement make other areas in the sub-region (e.g. Somali region of Ethiopia, north east Kenya, and Yemen) potentially at risk of international spread.

The new outbreak of cVDPV2 recently detected in Jigawa, Nigeria, again underlines the vulnerability of northern Nigeria to poliovirus transmission.


The Committee unanimously agreed that the risk of international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC), and recommended the extension of Temporary Recommendations for a further three months. The Committee considered the following factors in reaching this conclusion:

Although the risk of international spread of WPV may be diminishing as transmission falls, the impact of any delay in eradicating WPV caused by international spread, should it occur now, would be even more grave in terms of delaying certification and the need to maintain human and financial resources for a longer period to achieve eradication.The risk of global complacency developing increases as the numbers of WPV cases remains low and eradication becomes a tangible reality, and removing the PHEIC now could contribute to greater complacency, particularly at an inopportune time given the upcoming Hajj with its heightened population movement.

Many countries remain vulnerable to WPV importation, as evidenced by gaps in population immunity in several key high risk areas, and also the current number of cVDPV outbreaks, both type 2 and 3, which only emerge and circulate due to lack of polio population immunity.

Inaccessibility to vaccination programs remains another major risk, particularly in several countries currently infected with WPV or cVDPV, i.e. Afghanistan, Nigeria and Somalia, which all have sizable populations that have been unreached with polio vaccine for prolonged periods.

The risk is amplified by population movement, whether for family, social, economic or cultural reasons, or in the context of populations displaced by insecurity and returning refugees. There is a need for international coordination to address these risks, particularly between Afghanistan and Pakistan, Nigeria and its Lake Chad neighbors, and countries in and bordering the Horn of Africa and DR Congo.

The inaccessible population in Borno state in Nigeria remains substantial despite the commendable efforts to reach all settlements.These populations have not received polio vaccine since WPV1 was detected in 2016, so ongoing transmission in these unreached pockets cannot be ruled out. The risk of transmission in the Lake Chad sub-region appears considerable, with significant gaps in population immunity in these vulnerable countries, compounded by international population movement.

The new international outbreak of cVDPV2 affecting Somalia and Kenya, with a highly diverged cVDPV2 that appears to have circulated undetected for up to four years highlights that there are still high-risk populations in South and Central zones of Somalia where population immunity and surveillance are compromised by inaccessibility.

The ongoing spread of cVDPV2 in DR Congo demonstrates significant gaps in population immunity at a critical time in the polio endgame;the lack of IPV vaccination in several countries neighboring DR Congo heightens the risk of international spread, as population immunity is rapidly waning.

The increasing number of countries in which immunization systems have been weakened or disrupted by conflict and complex emergencies poses another risk. Populations in these fragile states are vulnerable to outbreaks of polio. Outbreaks in fragile states are exceedingly difficult to control and threaten the completion of global polio eradication during its end stage.

A regional approach and strong cross­border cooperation is required to respond to these risks, as much international spread of polio occurs over land borders.