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WHO worried about poliovirus, keeps 'international emergency' designation

Christian Fernsby ▼ | June 1, 2019
The twenty-first 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 14 May 2019 at WHO headquarters with members, advisers and invited Member States attending via teleconference, supported by the WHO secretariat.
Poliovirus vaccination
World   Poliovirus vaccination
The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polioviruses (cVDPV).

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 19 February 2019: Afghanistan, DR Congo, Indonesia, Nigeria, Pakistan and Somalia.

The committee commended all countries that presented on the quality of information provided, and the transparency with which countries discussed their challenges.

The Committee is gravely concerned by the significant further increase in WPV1 cases globally in 2019, particularly in Pakistan where 15 cases have already been reported.

In Pakistan transmission continues to be widespread, as indicated by the number of positive environmental isolates in many areas of the country, and the proportion of samples that detect WPV1 is rising.

The recent cluster of cases in Lahore also indicates that vulnerabilities still exist outside the high-risk corridors.

Notably, the increased rate of infection during what is usually the low season may herald even higher rates of infection in the coming high season unless urgent remedial steps are taken.

The committee was very concerned about attacks on vaccinators and on the police protecting them.

The increasing refusal by individuals and communities to accept vaccination also needs to be actively addressed.

While the committee understood that the recent elections and political transition may have adversely affected delivery of the polio program, it is now essential that the new government renews its efforts, noting that the eradication program in the country is no longer on-track.

Highlighting these concerns, the committee noted the recent detection of WPV1 in sewage in Iran in an area close to the international border with Pakistan.

Based on genetic sequencing, the virus is most closely linked to viruses found recently in Karachi, Pakistan.

While there is no evidence currently that transmission has occurred in Iran and routine immunization coverage is high there, this finding together with the resumption of WPV1 international spread between Pakistan and Afghanistan suggests that rising transmission in Pakistan correlates with increasing risk of WPV1 exportation beyond the single epidemiological block formed by the two countries.

The Iran event is the first such exportation detected since 2014 and signals that the hard fought gains of recent years can easily be reversed.

In Afghanistan, the critical issue of access is seriously hampering progress towards global eradication and needs to be resolved.

Inaccessible and missed children particularly in the Southern Region mean there is a large cohort of susceptible children in this part of Afghanistan.

Environmental surveillance has found an increased proportion of positive samples in 2019.

The security situation and access will need to significantly improve for eradication efforts to progress.

The Committee noted the continued high degree of cooperation and coordination between Afghanistan and Pakistan, particularly in reaching high risk mobile populations that frequently cross the international border and welcomed the all age vaccination now being taken at key border points between the two countries.

In Nigeria, there has been no WPV1 detected for over two and a half years, and it is possible that the African Region may be certified WPV free in early 2020.

However, this will require careful assessment of the risk of missed transmission in inaccessible areas of Borno, and in other countries in the region where confidence in surveillance is lacking.

The Committee commended the strong efforts to reach inaccessible and trapped children in Borno, Nigeria, even in the face of increased insecurity, and noted that the inaccessible target population was now down to around 60 000 children, scattered across Borno State in smaller pockets.

The committee noted the delays between case investigation and final laboratory results in Nigeria and suggested an analysis be undertaken to understand the reasons for this.

The multiple cVDPV2 outbreaks on the continent of Africa are as concerning as the WPV1 situation in Asia.

The emergence of new strains of cVDPV2 in areas where mOPV2 has been used, the recent spread of cVDPV2 into southern Nigeria, including the densely populated Lagos region, and evidence of missed transmission in Nigeria and Somalia suggests that the situation continues to deteriorate.

Insufficient coverage with IPV exacerbates the growing vulnerability on the continent to cVDPV2 transmission.

Early detection of any international spread from the five currently infected countries and prioritized use of mOPV2 is essential to mitigate further depletion of the limited mOPV2 supply.

Repeatedly, cases have occurred in border districts (in Nigeria, close to Benin, in DR Congo close to Angola, in Somalia, close to Ethiopia, and in Mozambique, close to Malawi).

The cVDPV1 outbreaks in PNG and Indonesia and cVDPV3 in Somalia highlight the gaps in population immunity due to pockets of persistently low routine immunization coverage in many parts of the world.

However, these outbreaks seem to pose a lesser risk of international spread, as bOPV vaccine is already available in the country, and available for traveler vaccination, and global population immunity is far higher than for type 2.

It appears likely there has been missed transmission of cVDPV1 in Indonesia although no evidence so far that the virus has spread beyond Papua.

Large inaccessible areas of Somalia are a significant constraint on achieving interruption of transmission, exacerbated by large nomadic population movements.

The committee noted that in all infected countries, routine immunization was weak, and coverage remains very poor in many areas of these countries.

Inaccessibility is a major risk to interruption of transmission in Nigeria, Niger, Somalia and Afghanistan, and conflict in these countries and DR Congo makes control of these outbreaks even more challenging.

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.