Abstract
Since May 2019, the Central African Republic has experienced a poliomyelitis outbreak caused by type 2 vaccine-derived polioviruses (VDPV-2s). The outbreak affected Bangui, the capital city, and 10 districts across the country. The outbreak resulted from several independent emergence events of VDPV-2s featuring recombinant genomes with complex mosaic genomes. The low number of mutations (<20) in the viral capsid protein 1–encoding region compared with the vaccine strain suggests that VDPV-2 had been circulating for a relatively short time (probably <3 years) before being isolated. Environmental surveillance, which relies on a limited number of sampling sites in the Central African Republic and does not cover the whole country, failed to detect the circulation of VDPV-2s before some had induced poliomyelitis in children.
Highlights
Since May 2019, the Central African Republic has experienced a poliomyelitis outbreak caused by type 2 vaccine-derived polioviruses (VDPV-2s)
Phylogenetic analysis based on viral capsid protein 1 (VP1)-encoding regions showed that the Central African Republic (CAR) VDPV-2s fell into different lineages (Figure 2, panel A; Appendix Figure https:// wwwnc.cdc.gov/EID/article/27/2/20-3173-App1. pdf)
The low nucleotide divergence observed within the VP1-encoding sequence between the CAR VDPV-2s and Sabin-2 makes the hypothesis of silent circulation of Sabin-2–derived strains originating from the trivalent oral polio vaccine (OPV) over >3 years unlikely
Summary
Since May 2019, the Central African Republic has experienced a poliomyelitis outbreak caused by type 2 vaccine-derived polioviruses (VDPV-2s). Since May 2019, the Central African Republic (CAR) has experienced a poliomyelitis outbreak caused by serotype Given the evolutionary rate of this genomic region (≈10−2 nucleotide changes/site/ year [5]), this range suggests that VDPVs had been circulating in CAR from a few months to a couple of years before detection.
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