Table 1 Case definitions

AFP case: An AFP case is a child < 15 years of age presenting with sudden onset of flaccid paralysis or muscle weakness due to any cause or any person of any age with paralytic illness if clinicians suspect poliomyelitis.

Confirmed polio case: A suspected AFP case with poliovirus isolation from a stool sample.

Compatible is an AFP case with inadequate samples and residual paralysis at 60 days follow-up investigation, and reviewed and classified by the National Polio Expert Committee (NPEC)

Non-polio AFP cases: A suspected AFP case with no poliovirus isolation from a stool sample or inadequate case reviewed and discarded by the NPEC.

Non-polio AFP rate: “number of discarded as NP-AFP cases in children < 15 years, divided by population < 15 years old multiplied by 100,000 per year”.

Stool adequacy: “the number of AFP cases with two stools collected ≤ 14 days after paralysis of onset, collected ≥ 24–48 hours apart, and arriving in “good condition at the laboratory divided by a total number of AFP cases, and multiplied by 100” Good condition” means that upon arrival: There is a temperature indicator (showing < 8 °C) in the container, with no desiccation or leakage and proper documentation [37]

Non- poliovirus Enterovirus: the other viruses present in stool apart from the poliovirus. Its presence in stool is an indication of adequacy of the stool sample

Discarded cases are non-polio AFP cases classified by the National Expert Committee after an in-depth review of the cases that exclude all WPV, VDPV, and compatible cases.

Inadequate cases: Cases detected over 14 days from the date onset of paralysis and arrival of the stool specimens to the laboratory in bad condition.

Investigation of AFP cases: An initial investigation of suspected AFP cases conducted by health workers and verified by trained field staff, using a standard case investigation form to capture demographic, clinical, and epidemiological information with 60-days follow-up investigation for inadequate cases.

Final classification: All reported inadequate AFP cases classified by the National Polio Expert Committee (NPEC) supported by the Secretariat. All adequate cases are classified automatically using a virological classification scheme with final approval of expert committee.