In a district that was recently certified as polio-free, a 4-year-old child develops acute flaccid paralysis (AFP). Stool samples are sent to the reference laboratory. Which finding would classify this as a Vaccine-Derived Poliovirus (VDPV) case rather than wild poliovirus?

• A Poliovirus type 2 isolated from stool identical to wild poliovirus type 2
• B Poliovirus type 1 isolated from stool with >1% nucleotide divergence from Sabin strain ✓
• C Absence of poliovirus in stool but AFP still present
• D Poliovirus isolated from stool with 0.3% divergence from Sabin strain

Explanation

Vaccine-Derived Poliovirus (VDPV) is defined as a poliovirus derived from the OPV Sabin strain with ≥1% nucleotide divergence (for type 1 and 3) or ≥0.6% divergence (for type 2, which has been replaced by novel OPV2/mOPV2). Less than 1% divergence (e.g., 0.3%) represents vaccine-like poliovirus (VDPV precursors). Wild poliovirus type 2 has been eradicated globally. Absence of poliovirus suggests a non-polio AFP cause.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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