ISLAMABAD: The Emergency Committee under the International Health Regulations on the international spread of poliovirus has warned that re-infection of epidemiologically-critical areas and historical reservoirs in Pakistan and Afghanistan represent a significant risk to the gains made during the last 18 months.

The emergency committee, in a statement issued in Geneva on Friday, says the risk of international spread of wild poliovirus remains since the actual spread of Type-1 Wild Poliovirus (WPV1) lineages seen predominantly in Afghanistan in 2022 now being detected in Pakistan in 2023. In this regard, the statement mentioned historical reservoirs like Karachi and the Quetta block in Pakistan and Kandahar in Afghanistan.

According to the statement, high-risk mobile populations in Pakistan represent a specific risk of international spread to Afghanistan in particular, compounded by the large number of returnees from Pakistan into various parts of Afghanistan.

The large pool of unvaccinated ‘zero dose’ children in southern Afghanistan also constitutes a major risk, while some areas in Afghanistan still only allow site to site or mosque to mosque immunisation response, which has been shown to be less effective than the house to house modality.

Two more samples in ‘imported cluster’ found positive

The statement says although it is likely transmission of WPV1 has been interrupted in Malawi and Mozambique, the route from Pakistan to Africa remains unknown. The committee expressed disappointment on the pockets of insecurity in the remaining endemic transmission zones.

There have been four new cases of WPV1 in Pakistan since the last meeting in August, bringing the total to six in 2023. There has been a large increase in environmental detection, with 60 positive samples found in the three months from September to November, bringing this year’s total to 82.

Detection

Two more environmental samples have been found positive for the polio virus, as according to sources in Pakistan’s National Polio Laboratory at the National Institute of Health (NIH), the lab has confirmed the detection of WPV1 in environmental (sewage) samples collected from Karachi South and Chaman districts. A health ministry official said the virus in both samples belonged to the imported virus cluster. “Samples of sewage water from the area are a basic parameter to determine the success of polio campaigns. Moreover, the presence of virus in sewage also shows that the immunity level of children in the area has fallen and they are at risk of catching the disease,” he added.

According to the IHR committee statement, new transmission is occurring in Quetta, Karachi, Islamabad-Rawalpindi and Peshawar blocks after a period of non-detection. Although implementation of a polio action plan in southern KP has resulted in 160,000 more children being vaccinated, the context remains challenging: political instability, insecurity in some areas, with front line workers requiring police patrols to accompany them, and vaccination boycotts where communities make demands for other services in exchange for allowing polio vaccination. The programme continues to miss a significant number of children in Pakistan.

Since the last meeting, there have been no new WPV1 cases reported from Afghanistan, where the total number of cases remains six, all from Nangarhar province. However, there have been 46 WPV1 positive environmental samples to date in 2023, mostly from the endemic East Region (Nangarhar and Kunar provinces), but recently also in environmental samples from Kabul, Kandahar, Zabul and Balkh provinces. This indicates spread of WPV1 from the endemic zones of Afghanistan (East Region) and Pakistan (South KP) and is a reversal of recent progress.

The programme is implementing high quality campaigns and reaching more children than ever before, but the quality will have to be increased further and sustained. Any setback in Afghanistan poses a risk to the programme in Pakistan due to high population movement.

The recent major increase in the number of Afghan returnees from Pakistan has compounded the challenges in Afghanistan, though close coordination is being maintained with UNHCR and IOM for vaccination at their centres and for information sharing. Districts with significant influx of returnees will be included in the upcoming polio vaccination campaigns, the statement says.

Published in Dawn, December 24th, 2023