Concerns over poliovirus spread: WHO to extend travel restrictions for another 3 months

ISLAMABAD: The World Health Organization (WHO) has decided to extend travel restrictions on Pakistan for another three months due to ongoing concerns about the spread of poliovirus.

This decision was made during the 41st meeting of the WHO Emergency Committee, held on March 6, where representatives from polio-affected countries, including Pakistan, participated via video link.

The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polioviruses (cVDPV) in the context of the global target of interruption and certification of WPV1 eradication by 2027 and interruption and certification of cVDPV2 elimination by 2029.

Technical updates were received about the situation in the following countries: Afghanistan, Algeria, Chad, Democratic Republic of the Congo (DR Congo), Djibouti, Ethiopia, Germany, Pakistan, Poland and the United Kingdom of Great Britain and Northern Ireland.

The committee assessed the global polio situation, with a particular focus on Pakistan’s current status and efforts to curb the virus. Despite acknowledging progress in the country’s anti-polio campaigns, the WHO noted that Pakistan and Afghanistan remain key obstacles in the path to global polio eradication and continue to be held responsible for the ongoing international transmission of the poliovirus.

While the WHO expressed confidence in Pakistan’s polio initiatives, it stressed the need for enhanced implementation at the provincial and district levels. A major concern was the sharp rise in polio-positive environmental samples in Pakistan — a 12-fold increase reported between 2023 and 2024.

So far in 2024, 628 environmental samples have tested positive for poliovirus across the country, with the virus spreading to new districts. The active circulation of the YB3A4A B-cluster strain remains a significant issue, particularly in Khyber Pakhtunkhwa (KP), Sindh, and Balochistan.

The cities of Karachi, Peshawar, and Quetta have emerged as hotspots for the wild poliovirus type 1 (WPV1), which continues to circulate in central Pakistan and southern KP. WHO expressed deep concern over this trend especially since WPV1 is now largely confined to Pakistan and Afghanistan globally.

The organisation also raised concerns about immunisation coverage, particularly given the virus’s spread during the low transmission season and the expected increase in cases during the upcoming high transmission period.

The WHO has urged the Pakistani government to ensure more effective polio campaigns in high-risk areas and highlighted the importance of addressing cross-border virus transmission, especially from southern KP and the Quetta block into Afghanistan.

The committee stressed that the movement of displaced persons and refugees is contributing to the virus’s spread. It called for enhanced vaccination efforts at Pakistan-Afghanistan border crossings and emphasized the need for strengthened bilateral coordination. Simultaneous anti-polio campaigns on both sides of the border were recommended as essential to breaking the chain of transmission.

Since the last Emergency Committee meeting, 36 new WPV1 cases were reported, three from Afghanistan and 33 from Pakistan bringing the total to 99 WPV1 cases in 2024 and three in 2025. This represents more than four-fold increase in Afghanistan and more than 12-fold increase in Pakistan in the number of WPV1 cases from 2023 to 2024. A total of 741 WPV1 positive environmental samples were reported in 2024, 113 from Afghanistan and 628 from Pakistan.

In 2025, 80 WPV1-positive environmental samples have been reported, nine from Afghanistan and 71 from Pakistan.

The upward trend in WPV1 cases and environmental detections has persisted in both endemic countries throughout 2024. In Pakistan, this increase has been evident since mid-2023, initially in environmental samples and later in paralytic polio cases, primarily in KP, Sindh, and Balochistan.

In Afghanistan, the rise in WPV1 detections, both in environmental samples and cases during 2024 has been predominantly in the South Region.

The Committee noted the geographic spread of WPV1 to new provinces and districts in both endemic countries in 2024 and observed that WPV1 transmission has re-established in historical reservoirs, including Kandahar (Afghanistan), Peshawar, Karachi, and Quetta Block (Pakistan).

Currently, the most intense WPV1 transmission is occurring in the southern cross-border epidemiological corridor, encompassing Quetta Block (Pakistan) and the South Region (Afghanistan).

The Committee also noted the ongoing WPV1 transmission in the epidemiologically critical South KP and Central Pakistan blocks of Pakistan.

Review of the molecular epidemiology indicates that there has been progressive elimination of the genetic cluster ‘YB3C’ in 2022 and 2023, with its last detection in November 2023 in Bannu district of KP province of Pakistan. However, there has been persistent transmission of YB3A genetic cluster since May 2022, resulting in its split into two: YB3A4A and YB3A4B.

During the first half of 2024, the cluster YB3A4A was mainly circulating in the northern and southern cross-border corridors. During the second half of 2024 there was distinct expansion of both these genetic clusters seen in Pakistan, more pronounced for YB3A4A, in Afghanistan, the predominantly circulating genetic cluster in YB3A4A.

Both Afghanistan and Pakistan continue to implement an intensive and mostly synchronized campaign schedule focusing on improved vaccination coverage in the endemic zones and effective and timely response to WPV1 detections elsewhere in each country. Afghanistan implemented five sub-national vaccination rounds during the second half of 2024, targeting infected and high-risk provinces, while Pakistan implemented two nationwide and a large scale sub-national vaccination round from September through December 2024.

After encouraging progress towards implementing house-to-house campaigns in all of Afghanistan during the first half of 2024, Afghanistan programme has not been able to implement house-to-house campaigns during most of the second half of 2024. All vaccination campaigns in Afghanistan since October 2024 have been implemented using alternate modalities (mostly site-to-site).

The committee was concerned that site-to-site campaigns are usually not able to reach all the children, especially those of younger age and girls, which may lead to a further upsurge of WPV1 with geographical spread in Afghanistan and beyond. Afghanistan programme is taking measures to maximize the reach of site-to-site campaigns through adequate operational and social mobilization measures.

The Committee noted overall high reported coverage of the vaccination campaigns in Pakistan; however, variations were observed about the quality at the sub-provincial and sub-district levels, relating to operational implementation challenges and increasing insecurity, particularly in the Khyber Pakhtunkhwa and Balochistan provinces. Nearly 200 000 and 50 000 missed children were reported from the South KP and Quetta Block (Balochistan) in Pakistan at the end of October and December 2024 campaigns.

In addition to seasonal movement patterns within and between the two endemic countries, the continued return of undocumented migrants from Pakistan to Afghanistan compounds the challenges faced.

The scale of the displacement increases the risk of cross-border poliovirus spread as well as spread within both the countries. This risk is being managed and mitigated in both countries through vaccination at border crossing points and the updating of micro-plans in the districts of origin and return.

The programme continues to closely coordinate with IOM and UNHCR. The Committee noted ongoing coordination between the programmes of Afghanistan and Pakistan at the national and sub-national levels.

In summary, the available data indicates that globally transmission of WPV1 is geographically limited to the two WPV1 endemic countries; however, there has been geographical spread and intensifying transmission within the two endemic countries in 2024.

Copyright Business Recorder, 2025