Polio still a public health emergency, declares WHO.
The World Health Organization has highlighted that the spread of polio must still be classified as a public health emergency because, after years of major gains, the fight to eradicate polio is facing setbacks marked by an increase in wild poliovirus type 1 cases in Afghanistan, stagnation in Pakistan, and the spread of circulating vaccine-derived poliovirus in several countries.
The Emergency Committee under the International Health Regulations (2005) (IHR) regarding the international spread of poliovirus reviewed the data on wild poliovirus (WPV1) and circulating vaccine-derived polioviruses (cVDPV).
“The ongoing situation we find ourselves in continues to require that a public health emergency of international concern should be applied”, Helen Rees, chair of the International Health Regulations (IHR) Emergency Committee Regarding the International Spread of Poliovirus.
The 12-member committee “unanimously agreed” on the risk assessment during its 19th meeting on Nov 27 and recommended the extension of the emergency designation for a further 3 months, a decision that was agreed upon by WHO Director-General Tedros Adhanom Ghebreyesus.
The Committee was very concerned by the increase in WPV1 cases globally in 2018, especially regarding the increased number of WPV cases in Afghanistan. Furthermore, after a 10-month period of no international spread of wild poliovirus between the two neighbors, Pakistan and Afghanistan, cross-border spread in both directions has occurred in the last three months.
In Pakistan, the situation in 2018 has stagnated, with the number of cases so far at the same level in 2018 as for the whole of 2017. Furthermore, positive environmental isolates in 2018 continue to be widely spread geographically indicating multiple areas of transmission and missed susceptible population groups. Nevertheless, the performance of the eradication program has shown some improvement in areas such as SIA quality.
In Afghanistan, the number of polio cases has almost doubled in 2018, with 19 cases reported so far, compared to 10 at the same time last year, due to worsened security and greater inaccessibility, and persistent pockets of refusals and missed children.
Michel Zaffran, WHO director for polio eradication, said globally, there had been 28 cases of wild poliovirus so far this year, compared with 22 last year. This number included 20 cases reported in Afghanistan (double the number of cases as of this time last year) and eight cases in Pakistan.
The numbers show that “we are stagnating and not reducing”, Zaffran said. “We continue to see the circulation of the virus in several places in Pakistan and Afghanistan as per the environmental [sewerage] sampling data that we collect [from 50 sites in high-risk areas in Pakistan and between 15–20 in Afghanistan]”, he said.
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 declaration of the PHEIC and issuance of Temporary Recommendations has reduced the risk of international spread of WPV, progress is fragile, and should international spread now occur, the impact on WPV eradication would be even more grave in terms of delaying certification and prolonging requirements for dedicated human and financial resources in support of the eradication effort. The reversal in progress in Afghanistan and the stagnation in Pakistan with the exportation of WPV continuing between the two countries, heighten concerns.
- There is a risk of global complacency as the numbers of WPV cases remains low and eradication becomes a tangible reality and a concern that removal of the PHEIC now could contribute to greater complacency.
- Many countries remain vulnerable to WPV importation. Gaps in population immunity in several key high-risk areas are evidenced by the current number of cVDPV outbreaks of all serotypes, which only emerge and circulate when polio population immunity is low as a result of deficient routine immunization programmes.
- The 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 conflict.
- Similarly, the new spread of cVDPV2 between Nigeria and Niger highlights the significant risk of persisting type 2 outbreaks two years after OPV2 withdrawal, and the inability so far to prevent further spread within and outside Nigeria through the application of consistently high-quality mOPV2 SIAs is a concern.
- The difficulty in controlling the spread of cVDPV2 in DR Congo heightens these concerns and demonstrates significant gaps in population immunity at a critical time in polio endgame;the low coverage with routine IPV vaccination in several countries neighbouring DR Congo heightens the risk of international spread, as population immunity is rapidly waning.
- Inaccessibility continues to be a 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 increasing number of countries in which immunization systems have been weakened or disrupted by conflict and complex emergencies pose another risk. Populations in these fragile states are vulnerable to outbreaks of polio.
- 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. A regional approach and strong crossborder cooperation are required to respond to these risks, as the much international spread of polio occurs over land borders.
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