Polio Cases in Pakistan 2016 — Twenty Cases and a Narrowing Map

Pakistan recorded 20 wild poliovirus cases in 2016, continuing the steep decline that began after the 2014 peak of 306. For the first time since the outbreak years, transmission was confined to a genuinely small number of districts.

A narrowing map

The significance of 2016 is geographic as much as numerical. Cases clustered in the three historical reservoirs — the Karachi corridor in Sindh, the Quetta block in Balochistan, and the Peshawar–Khyber–tribal-areas belt in the north-west. Large parts of the country recorded no cases at all, and Punjab, home to more than half the population, was effectively clear.

This is the pattern that has defined every subsequent year: polio in Pakistan is not a national problem evenly distributed, but a persistent problem in a handful of specific places. The high-risk area classification is built directly on this observation.

The global switch

April 2016 brought the largest coordinated vaccine change in history. Following the certified eradication of wild poliovirus type 2 in 2015, every OPV-using country in the world — Pakistan included — withdrew trivalent oral polio vaccine within a two-week window and switched to bivalent OPV covering types 1 and 3. Inactivated polio vaccine was introduced into routine immunisation to maintain type 2 protection.

The switch removed the main source of type 2 vaccine-derived poliovirus, but it also meant that children born afterwards depended on IPV in routine immunisation for type 2 immunity — one reason routine coverage matters as much as campaigns.

Environmental surveillance keeps the pressure on

Even as case numbers fell, sewage sampling continued to detect poliovirus in major cities, confirming that transmission persisted below the level that paralysis reporting alone could reveal. That gap between visible cases and detected virus is precisely why the programme does not treat a low case count as proof of interruption. See polio surveillance in Pakistan.

Where 2016 sits in the record

2016's 20 cases were followed by 8 in 2017 — the lowest total Pakistan had ever recorded at that point. The full series is on the province-wise cases page.