Journal of Tropical Diseases and Parasitology ›› 2026, Vol. 24 ›› Issue (3): 188-193.doi: 10.20199/j.issn.1672-2302.2026.03.011

• EXPERIMENTAL STUDY • Previous Articles    

Molecular tracing analysis of vaccine-associated polioviruses based on the Markov Chain Monte Carlo algorithm

CHAI Yu1(), CHEN Wei2, CHENG Xiaodong1, SU Ying1, HE Jiali1, LUO Jing3, WANG Binbing1, WANG Zhijun2, DONG Zilu3, WANG Xin1, DONG Yan1, XU Qinghua1()   

  1. 1 Anhui Provincial Center for Disease Control and Prevention, Hefei 230601, Anhui Province, China
    2 Xiaoxian Center for Disease Control and Prevention
    3 Suzhou Center for Disease Control and Prevention
  • Received:2025-10-30 Online:2026-06-20 Published:2026-07-31
  • Contact: XU Qinghua, E-mail: xqh1126@sina.com

Abstract:

Objective To calculate the initial origin time of vaccine-associated poliovirus (PVa) and infer the source of the strain. Methods The viral VP1 sequence was obtained through cell culture and sequencing of type Ⅰ and type Ⅲ PVa isolated from a child’s fecal specimen. Then, based on VP1 region nucleotide sequences of type Ⅰ and Ⅲ poliovirus vaccine strains with documented evolutionary histories, the evolutionary rates for each type were calculated using a Markov Chain Monte Carlo (MCMC) model, from which the initial origin time of PVa was further estimated accordingly. Results Two strains of type Ⅰ PVa and four strains of type Ⅲ PVa were detected in the stool samples of this child. The initial origin time of type Ⅰ was from December 2021 to March 2022, and type Ⅲ, from August to November 2022, all of which were earlier than the date of administering the bivalent oral poliovirus vaccine (OPV) on February 28, 2023. No PVa was detected in the stool samples of the close contacts of this child. Conclusion Although MCMC model can provide a novel idea for estimating the initial origin time of PVa, yet its scientific validity still requires further verifying.

Key words: Vaccine-associated poliovirus, Sequencing, Tracing, Markov Chain Monte Carlo model

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