A 7-year-old child develops acute flaccid paralysis (AFP) of the right leg over 48 hours, with fever that resolved before paralysis onset. CSF shows normal protein, normal glucose, and mild lymphocytic pleocytosis. The child received 3 doses of OPV in infancy but not the fourth dose. Which of the following BEST distinguishes wild poliovirus AFP from vaccine-derived poliovirus (VDPV) AFP?
- A Presence of CSF lymphocytosis favors wild poliovirus
- B Wild poliovirus AFP typically recovers fully within 60 days
- C Stool viral isolation and sequence analysis showing >1% divergence from Sabin strain indicates VDPV ✓
- D Asymmetric paralysis occurs only with VDPV, not wild virus
Correct answer: C. Stool viral isolation and sequence analysis showing >1% divergence from Sabin strain indicates VDPV
Explanation
Vaccine-derived poliovirus (VDPV) is defined by greater than 1% nucleotide divergence from the corresponding Sabin OPV strain in VP1 capsid gene sequencing, implying prolonged replication and reversion toward neurovirulence. Wild poliovirus and VDPV cause clinically indistinguishable AFP, and stool PCR with sequencing remains the only definitive method of differentiation. Both cause asymmetric flaccid paralysis; residual paralysis at 60 days confirms non-Guillain-Barré etiology but does not distinguish wild from VDPV.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.