Environmental Surveillance Results — July 2025

Pakistan's environmental surveillance results for July 2025 report wild poliovirus type 1 detections across the national sewage sampling network, at the point in the year when transmission is at its most intense.

July is the sharpest month

Pakistan's poliovirus transmission season peaks in the second half of the year. July results therefore represent the virus close to its maximum circulation — and they are the results that most directly determine how many cases will be confirmed in the months that follow, because paralysis appears weeks after infection.

2025 closed with 31 confirmed cases, against 74 in 2024. The mid-year tally had stood at 14.

What the sampling network sees

Well over a hundred fixed sites nationwide, sampled on a regular cycle and tested at the WHO-accredited Regional Reference Laboratory at the National Institute of Health in Islamabad. Because roughly 199 of every 200 poliovirus infections cause no paralysis, sewage sampling detects a volume of transmission that case reporting alone cannot represent.

Reading peak-season results

• Breadth. How many provinces are returning positives. Transmission confined to known reservoirs is a very different situation from positives appearing across four provinces.
• New sites. A site positive after a long negative run indicates the virus expanding into territory where immunity may have drifted.
• Persistence. Sites positive month after month indicate established local transmission rather than transient introduction.
• Sequencing. Genetic links between positives and confirmed cases map the actual transmission routes, including movement across the Afghan border.

What the programme does with peak-season data

Peak-season positives drive the timing and targeting of the campaign rounds that follow. The logic is that a round delivered into a catchment where the virus has just been detected does considerably more than the same round delivered somewhere quiet — which is why environmental results, not case counts, increasingly set the campaign calendar.

The honest reading

A year that improves from 74 cases to 31 is a real achievement. A year in which sewage samples keep testing positive across multiple provinces is also a year in which the virus has not been interrupted. Certification requires three consecutive years with no wild poliovirus detected in people or in the environment.

For families

Vaccinate every child under five in every round, particularly during the high season when transmission is at its peak. Call 1166 if a team does not reach you.

Related: May surveillance results · how surveillance works