Published On: Tue, Aug 30th, 2016

WHO statement on the international spread of poliovirus

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IHR Emergency Committee recommendations regarding the international spread of poliovirus

The tenth meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) regarding the international spread of poliovirus was convened via teleconference by the WHO Director-General on 11 August 2016.

The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine­derived polioviruses (cVDPV).

The Secretariat presented a full report of progress for all affected IHR States Parties previously considered by the Emergency Committee. The following IHR States Parties presented an update on the implementation of the WHO Temporary Recommendations since the Committee last met on 12 May 2016: Afghanistan, Pakistan, and Nigeria.

Wild polio

The Committee was gravely concerned by the report from Nigeria of two new cases in July of acute flaccid paralysis in children due to WPV1 from Borno State from two different local government areas (LGA): Gwoza and Jere. The Committee noted that genetic analysis indicated that the two viruses detected had circulated undetected for several years. These cases, together with the cVDPV2 reported in May 2016 also from Borno, indicate polioviruses have been circulating undetected in the area for several years and that significant gaps in surveillance remain. Such gaps are compounded by a recent increase in the area of inaccessibility in the state. The Committee was also concerned that Gwoza district has a long border with the Extreme North province of Cameroon and is considered inaccessible. Noting the history of poliovirus transmission in the Lake Chad area, and the international borders around Borno with Cameroon, Chad and Niger, the Committee concluded that the risk of international spread between these four countries was extremely high and may already be happening. Further international spread would significantly delay progress towards global eradication. The Emergency Committee was concerned that the Nigerian Polio Presidential Committee has not met in 2016, and that there have been delays in government funds being released for the polio response.

The Committee applauded the progress being made in Afghanistan and Pakistan, and the renewed emphasis on cooperation along the long international border between the two countries noting that this constitutes an epidemiological block between the two countries. The Committee applauded the strong progress being made in Pakistan, with consistent evidence of reduced transmission in 2016, and welcomed Pakistan’s determination to complete eradication this year. The Committee was pleased that as a result of these efforts, there has been no international spread of wild poliovirus between Pakistan and Afghanistan since the previous meeting.

Whilst border vaccination between these two countries is limited to children under ten years of age, efforts are being made to vaccinate departing travellers of all age groups from airports. The committee was pleased that progress had been made in Afghanistan where some foreign embassies now facilitate implementation of Temporary Recommendations through adopting procedures that include proof of polio vaccination as part of visa application processes for travellers departing from Afghanistan.

The Committee, however, was concerned by the deteriorating security in parts of Afghanistan leading to more children becoming inaccessible, heightening anxiety about completion of eradication in 2016, thereby delaying the global polio endgame. The Committee also noted that globally there are still significant vulnerable areas and populations that are inadequately immunized due to conflict, insecurity and poor coverage associated with weak immunization programmes. Such vulnerable areas include countries in the Middle East, the Horn of Africa, and Central Africa.

The Committee noted that in Equatorial Guinea (last case 3 May 2014) and Cameroon (last case 9 July 2014), although more than 24 months have passed without new infection by poliovirus, neither country had yet provided a final report as requested. Furthermore, Equatorial Guinea had weak surveillance indicators, and there were concerns about routine immunisation and Cameroon is now vulnerable to importation of WPV from Nigeria.

Vaccine derived poliovirus

The Committee noted that there have been no new cases of cVDPV since the previous meeting in May 2016.

In Guinea, the outbreak appears to be confined to one region, Kankan, where the most recent case had onset in December 2015. The Committee, however, felt there appears to be a medium to high risk of spread to neighbouring areas, as active surveillance has only recently started and the likelihood of missing transmission cannot be ruled out. Furthermore, surveillance indicators in neighbouring Liberia and Sierra Leone are below required standards and more efforts are needed to enhance surveillance in all these countries.

The Committee remains very concerned that in Nigeria a circulating vaccine-derived poliovirus type 2 (cVDPV2) has been detected in an environmental sample in March 2016 in Maiduguri, Borno State, north-east Nigeria. The Committee noted that a very robust outbreak response is under way by the Government of Nigeria, but the new incidence of WPV1 now complicates that response.

In Myanmar, Laos and Madagascar, where the most recent cases had onset of paralysis on : 5 October 2015 from Rakhine province, 11 January 2016 from Vientiane province, and 22 August 2015 from Sud-Ouest province, respectively, recent outbreak assessments showed much progress, but uncertainty about ongoing transmission remains due to gaps in surveillance.

In the Ukraine, where two cases of cVDPV1 occurred in 2015, the outbreak assessment recently concluded that poliovirus transmission had ceased, and as it is now 13 months since onset of the last case (7 July 2015) the outbreak is considered closed.

Conclusion

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

  • The new outbreak of WPV1 in Nigeria highlighting that there are high-risk areas where surveillance is compromised by inaccessibility, resulting in ongoing circulation of WPV for several years without detection. The risk of transmission in the Lake Chad sub-region appears extremely high.
  • The continued international spread of wild poliovirus during 2015 and 2016 involving Pakistan and Afghanistan.
  • The current special and extraordinary context of being closer to polio eradication than ever before in history.
  • The risk and consequent costs of failure to eradicate globally one of the world’s most serious vaccine preventable diseases. Even though global transmission has fallen dramatically and with it the likelihood of international spread, the consequences and impact of international spread should it occur would be grave.
  • The possibility of global complacency developing as the numbers of polio cases continues to fall and eradication becomes a possibility.
  • The continued necessity of a coordinated international response to improve immunization and surveillance for wild poliovirus, to stop international spread and reduce the risk of new spread.
  • The serious consequences of further international spread for the increasing number of countries in which immunization systems have been weakened or disrupted by conflict and complex emergencies. 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.
  • The importance of a regional approach and strong cross­border cooperation, as much international spread of polio occurs over land borders, while recognizing that the risk of distant international spread remains from zones with active poliovirus transmission.
  • Additionally with respect to cVDPV:
    • cVDPVs also pose a risk for international spread, which without an urgent response with appropriate measures threatens vulnerable populations as noted above;
    • The emergence and circulation of VDPVs in four WHO regions demonstrates significant gaps in population immunity at a critical time in the polio endgame;
    • There is a particular urgency of preventing type 2 cVDPVs following the globally synchronized withdrawal of type 2 component of the oral poliovirus vaccine in April 2016;
    • The ongoing challenges of improving routine immunization in areas affected by insecurity and other emergencies, including Ebola;
    • The global shortage of IPV poses fresh challenges.

Risk categories

The Committee provided the WHO Director­General with the following advice aimed at reducing the risk of international spread of wild poliovirus and cVDPVs, based on the risk stratification as follows:

Wild poliovirus

  • States currently exporting wild poliovirus;
  • States infected with wild poliovirus but not currently exporting;
  • States no longer infected by wild poliovirus, but which remain vulnerable to international spread.

Circulating vaccine derived poliovirus

  • States currently exporting cVDPV;
  • States infected with cVDPV but not currently exporting;
  • States no longer infected by cVDPV, but which remain vulnerable to the emergence and circulation of VDPV.

The Committee applied the following criteria to assess the period for detection of no new exportations and the period for detection of no new cases or environmental isolates of wild poliovirus or cVDPV:

Criteria to assess States no longer exporting (detection of no new wild poliovirus or cVDPV exportation)

  • Poliovirus Case: 12 months after the onset date of the first case caused by the most recent exportation PLUS one month to account for case detection, investigation, laboratory testing and reporting period, OR when all reported AFP cases with onset within 12 months of the first case caused by the most recent importation have been tested for polio and excluded for newly imported WPV1 or cVDPV, and environmental samples collected within 12 months of the first case have also tested negative, whichever is the longer.
  • Environmental isolation of exported poliovirus: 12 months after collection of the first positive environmental sample in the country that received the new exportation PLUS one month to account for the laboratory testing and reporting period.
Criteria to assess States no longer infected (detection of no new wild poliovirus or cVDPV)
  • Poliovirus Case: 12 months after the onset date of the most recent case PLUS one month to account for case detection, investigation, laboratory testing and reporting period OR when all reported AFP cases with onset within 12 months of last case have been tested for polio and excluded for WPV1 or cVDPV, and environmental samples collected within 12 months of the last case have also tested negative, whichever is the longer.
  • Environmental isolation of wild poliovirus or cVDPV (no poliovirus case): 12 months after collection of the most recent positive environmental sample PLUS one month to account for the laboratory testing and reporting period

Temporary recommendations

States currently exporting wild poliovirus or cVDPV

Currently Pakistan (last wild poliovirus exportation: 1 February 2016) and Afghanistan (last wild poliovirus exportation: 6 June 2015).

Exporting countries should:

  • Officially declare, if not already done, at the level of head of state or government, that the interruption of poliovirus transmission is a national public health emergency; where such declaration has already been made, this emergency status should be maintained.
  • Ensure that all residents and long­term visitors (i.e. > four weeks) of all ages receive a dose of oral poliovirus vaccine (OPV) or inactivated poliovirus vaccine (IPV) between four weeks and 12 months prior to international travel.
  • Ensure that those undertaking urgent travel (i.e. within four weeks), who have not received a dose of OPV or IPV in the previous four weeks to 12 months, receive a dose of polio vaccine at least by the time of departure as this will still provide benefit, particularly for frequent travellers.
  • Ensure that such travellers are provided with an International Certificate of Vaccination or Prophylaxis in the form specified in Annex 6 of the IHR to record their polio vaccination and serve as proof of vaccination.
  • Restrict at the point of departure the international travel of any resident lacking documentation of appropriate polio vaccination. These recommendations apply to international travellers from all points of departure, irrespective of the means of conveyance (e.g. road, air, sea).
  • Recognising that the movement of people across the border between Pakistan and Afghanistan continues to facilitate exportation of wild poliovirus, both countries should further intensify cross­border efforts by significantly improving coordination at the national, regional and local levels to substantially increase vaccination coverage of travellers crossing the border and of high risk cross­border populations. Both countries have maintained permanent vaccination teams at the main border crossings for many years. Improved coordination of cross­border efforts should include closer supervision and monitoring of the quality of vaccination at border transit points, as well as tracking of the proportion of travellers that are identified as unvaccinated after they have crossed the border.
  • Maintain these measures until the following criteria have been met: (i) at least six months have passed without new exportations and (ii) there is documentation of full application of high quality eradication activities in all infected and high risk areas; in the absence of such documentation these measures should be maintained until the state meets the above criteria of a ‘state no longer exporting’.
  • Provide to the WHO Director­General a monthly report on the implementation of the Temporary Recommendations on international travel, including the number of residents whose travel was restricted and the number of travellers who were vaccinated and provided appropriate documentation at the point of departure.
States infected with wild poliovirus or cVDPVs but not currently exporting

Infected countries (WPV1)

  • Nigeria (last case 13 July 2016)

Infected countries (cVDPV)

  • Nigeria (last env isolate 23 March 2016)
  • Guinea (last case 14 December 2015)
  • Madagascar (last case 22 August 2015)
  • Lao People’s Democratic Republic (last case 11 January 2016)
  • Myanmar (last case 5 October 2015)

These countries should:

  • Officially declare, if not already done, at the level of head of state or government, that the interruption of poliovirus transmission is a national public health emergency; where such declaration has already been made, this emergency status should be maintained.
  • Encourage residents and long­term visitors to receive a dose of OPV or IPV four weeks to 12 months prior to international travel; those undertaking urgent travel (i.e. within four weeks) should be encouraged to receive a dose at least by the time of departure.
  • Ensure that travellers who receive such vaccination have access to an appropriate document to record their polio vaccination status. Intensify regional cooperation and cross­border coordination to enhance surveillance for prompt detection of poliovirus and substantially increase vaccination coverage among refugees, travellers and cross­border populations.
  • Maintain these measures until the following criteria have been met: (i) at least six months have passed without the detection of wild poliovirus transmission or circulation of VDPV in the country from any source, and (ii) there is documentation of full application of high quality eradication activities in all infected and high risk areas; in the absence of such documentation these measures should be maintained until the state meets the criteria of a ‘state no longer infected’.
  • At the end of 12 months without evidence of transmission, provide a report to the WHO Director­General on measures taken to implement the Temporary Recommendations.
States no longer infected by wild poliovirus or cVDPV, but which remain vulnerable to international spread, and states that are vulnerable to the emergence and circulation of VDPV

Currently Somalia, Equatorial Guinea, Cameroon, Niger*, Chad* (WPV1) and Ukraine (cVDPV1)

These countries should:

  • Urgently strengthen routine immunization to boost population immunity.
  • Enhance surveillance quality to reduce the risk of undetected wild poliovirus and cVDPV transmission, particularly among high risk mobile and vulnerable populations.
  • Intensify efforts to ensure vaccination of mobile and cross­border populations, Internally Displaced Persons, refugees and other vulnerable groups.
  • Enhance regional cooperation and cross border coordination to ensure prompt detection of wild poliovirus and cVDPV, and vaccination of high risk population groups.
  • Maintain these measures with documentation of full application of high quality surveillance and vaccination activities.
  • At the end of 12 months without evidence of reintroduction of wild poliovirus or new emergence and circulation of cVDPV, provide a report to the Director General on measures taken to implement the Temporary Recommendations.

These countries should provide a final report as per the table below:

 

Country Most recent case onset / +ve environmental isolate Final Report due
Equatorial Guinea 3 May 2014 June 2016**
Cameroon 9 July 2014 August 2016**
Somalia 11 August 2014 Septmeber 2016
Ukraine 7 July 2015 August 2017

*Niger and Chad have not previously been subject to Temporary Recommendations, but the Committee concluded that the extraordinary circumstances in Nigeria made these countries (and Cameroon) highly vulnerable, and the Temporary Recommendations for vulnerable countries were appropriate to limit the risk of international spread.

**Reports overdue; however the epidemiological situation indicates heightened vulnerability currently.

Additional considerations for all infected countries

The Committee strongly urged global partners in polio eradication to provide optimal support to all infected countries at this critical time in the polio eradication program for implementation of the Temporary Recommendations under the IHR. Recognizing that cVDPV illustrates serious gaps in routine immunization programs in otherwise polio free countries, the Committee recommended that the international partners in routine immunization, for example Gavi, should urgently assist affected countries to improve the national immunization program. Investment in regional mechanisms such as the recent formation of a polio joint task force for Lake Chad is needed.

The Committee reviewed an analysis of the public health benefits and costs of implementing temporary recommendations that require exporting countries to vaccinate all international travellers before departure. The initial analysis suggests that this approach is cost-effective as there is ample evidence that air travelers may transmit polio and that vaccinating them would be effective in preventing international long distance spread. The committee requested further analysis around the cost-benefits of this approach including consideration of the opportunity costs that may result from diverting human resources to implement airport immunisation interventions. Notwithstanding this, the committee noted that as both Pakistan and Afghanistan have significant numbers of migrant workers utilizing air travel, implementation of these international travel recommendations are justifiable, and should continue to be supported by the countries and by partner agencies.

The Committee urged all countries to avoid complacency which could easily lead to a polio resurgence. Surveillance particularly needs careful attention to quickly detect any resurgent transmission.

Based on the advice concerning wild poliovirus and cVDPV, and the reports made by Afghanistan, Pakistan, and Nigeria, the WHO Director­General accepted the Committee’s assessment and on 22 August 2016 determined that the events relating to poliovirus continue to constitute a PHEIC, with respect to wild poliovirus and cVDPV. The WHO Director­General endorsed the Committee’s recommendations for countries falling into the definition of ‘States currently exporting wild polioviruses or cVDPV’, for ‘States infected with wild poliovirus or cVDPV but not currently exporting’ and for ‘States no longer infected by wild poliovirus, but which remain vulnerable to international spread, and states that are vulnerable to the emergence and circulation of VDPV’ and extended the Temporary Recommendations as revised by the Committee under the IHR to reduce the international spread of poliovirus, effective 22 August 2016.

The WHO Director­General thanked the Committee Members and Advisors for their advice and requested their reassessment of this situation within the next three months.

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WHO statement on the international spread of poliovirus