WPV1 Found in Sewage Samples from Attock and South Waziristan Lower

Wild poliovirus type 1 was detected in environmental (sewage) samples collected from Attock in Punjab and South Waziristan Lower in Khyber Pakhtunkhwa.

Why a sewage result is news

Roughly one poliovirus infection in two hundred causes paralysis. The other 199 produce mild illness or no symptoms at all, while the infected child still sheds virus in their stool for weeks. That is the single fact that makes environmental surveillance so valuable: sampling sewage detects the virus in a community whether or not anyone has been paralysed.

A positive environmental sample is therefore an early warning. It means poliovirus is circulating among children in that catchment now, and it typically arrives weeks before a case would appear — which is precisely when intervention is most useful.

The two locations

South Waziristan Lower sits in the southern Khyber Pakhtunkhwa corridor that has produced most of Pakistan's recent cases. A positive sample there confirms continued circulation in a known reservoir where security-related access constraints repeatedly interrupt campaigns.

Attock is different, and more concerning in one specific way. It lies in Punjab, the province with by far the largest population and one that has been effectively clear of polio for most of the past decade. Detection there indicates virus moving along transit routes into areas where population immunity may have drifted downward precisely because nobody has seen a case.

Attock sits on the main corridor between Khyber Pakhtunkhwa and Punjab, which is consistent with importation via population movement rather than long-established local transmission.

What happens after a positive sample

• Genetic sequencing, to establish where the virus came from and how closely it is related to strains found elsewhere.
• Targeted vaccination campaigns in the catchment area of the positive site.
• Intensified acute flaccid paralysis surveillance locally, actively searching for cases that may not have been reported.
• Increased sampling frequency to track whether circulation continues or stops.

How the network operates

Pakistan maintains an environmental surveillance network of well over a hundred fixed sampling sites nationwide, with samples tested at the WHO-accredited Regional Reference Laboratory at the National Institute of Health in Islamabad. The full method is described on the surveillance page.

For families in these districts

A positive sewage sample means the virus is in your community even if no child has been paralysed. Vaccinate every child under five in the next round without exception, and complete the routine immunisation schedule. Call 1166 if a team does not reach you.

Related: poliovirus in sewage across eight cities · district-wise cases