Pakistan Reports Polio Case After Nearly 15 Months

Pakistan confirmed a wild poliovirus case after nearly 15 months without one — at the time, the longest case-free stretch the country had ever recorded.

The period that preceded it

2021 closed with a single wild poliovirus case for the entire year. That was, and remains, the closest Pakistan has come to zero. The months that followed were the most optimistic period in the programme's history, and there was legitimate discussion of whether transmission had finally been interrupted.

The new case ended that. It came from the southern Khyber Pakhtunkhwa area that has since accounted for the majority of Pakistan's cases, and genetic sequencing of these isolates indicated that the virus had not been reintroduced from elsewhere — it had been circulating within Pakistan, undetected by paralysis reporting, the whole time.

Why a quiet period is not proof

This is the single most important lesson in the record. Because roughly one poliovirus infection in two hundred causes paralysis, a virus circulating at low levels in a well-immunised population can go many months without paralysing anyone. Case counts measure visible harm; they do not measure the presence of the virus.

What does measure presence is environmental surveillance — sewage sampling at fixed sites across the country. Through the case-free period, environmental samples continued to return positive results. The programme knew the virus was still there before the case appeared, which is precisely what the system exists to do. See polio surveillance in Pakistan.

What certification actually requires

A region can only be certified polio-free after at least three consecutive years with no wild poliovirus detected in people or in the environment, with surveillance sensitive enough to be credible. Fifteen months without a case is an encouraging signal. It is not a fifth of the way to certification if sewage is still testing positive.

What happened next

2022 closed with 20 cases, 2023 with six, and 2024 with 74. The volatility of that sequence is the strongest available evidence that the last chains of transmission in Pakistan are concentrated in a small number of districts where access and campaign quality determine everything.

For parents

The temptation during a quiet period is to assume the danger has passed. It has not. Two drops for every child under five in every round, and the complete routine immunisation schedule. Call 1166 if a team does not reach you.

Related: eradication within reach · cases by province