Acute Flaccid Paralysis (AFP) Surveillance in Pakistan

Surveillance is an ongoing systematic collection, analysis and interpretation of data and the dissemination of information to those who need to know so that appropriate action can be taken. The information is used for the planning, implementation and evaluation of public health interventions and programs.
Acute Flaccid Paralysis (AFP) is the recent or sudden onset of floppy paralysis or muscle weakness in a child aged less than 15 years of age, due to any cause; or any paralytic illness in a person of any age in whom a clinician suspects polio.

Acute Flaccid Paralysis surveillance is one of the four cornerstone strategies of polio eradication which seeks to identify all cases of polio through a system that targets any case of acute flaccid paralysis as a potential case of polio. The main objective of AFP surveillance is to detect the presence of circulating wild-type poliovirus. However, information obtained through surveillance has other essential uses. AFP surveillance data are the final measure of a country's progress towards polio eradication. It allows program managers to plan effective strategies for national immunization campaigns and supplemental activities.

In Pakistan, AFP surveillance began in 1997, but was given focused attention in 2000. As confirmed by international reviews, Pakistan has a well-functioning and sensitive AFP surveillance system at national, provincial, and district levels. The system has achieved and maintained all indicators above the internationally agreed standards for certification since 2001.
AFP Surveillance is conducted through passive (Zero Reporting) and active (Active Surveillance) mechanisms. The system operates as per defined standard operating procedures with set timelines quality monitoring indicators.

The best available method to confirm the diagnosis of poliomyelitis is the isolation and identification of poliovirus from the stool. The World Health Organization (WHO) has developed a global network of laboratories to provide this service in collaboration with several other institutions. The virology laboratory at NIH Islamabad is the Regional Reference Laboratory (RRL) for polio eradication and continues to demonstrate very high standards of quality control and meeting the international targets for accuracy. The RRL will also play a key role in certification of polio eradication by verifying the absence of wild poliovirus circulation.

Monitoring of performance indicators is critical to identify gaps and plug them. Two key surveillance indicators are of particular importance and meant to be thoroughly assessed for certification; 

Non-polio AFP rate: At least one case of non-polio AFP should be detected annually per 100 000 population aged less than 15 years. In endemic regions, to ensure even higher sensitivity, this rate should be two per 100 000.

Proportion of cases with two adequate stool specimens: at least 80% of AFP cases having ‘adequate’ stool specimens collected. ‘Adequate’ stool specimens are two stool specimens of sufficient quantity for laboratory analysis, collected at least 24 hours apart, within 14 days after the onset of paralysis, and arriving in the laboratory by reverse cold chain and with proper documentation.

Environmental Surveillance for Polio in Pakistan

Since 2009, The Polio Eradication Program in Pakistan complements its AFP surveillance system with environmental surveillance to detect polioviruses in sewage water in strategic locations. Environmental surveillance for polio is done in large cities of the four major provinces. Currently, 45 environmental surveillance sites have been designated in 17 districts/towns. Environmental surveillance has been helpful in better understanding the patterns of poliovirus circulation in the country and improved tailoring of vaccination strategies.