Recent emergence of vaccine-derived poliovirus type 2 in Senegal and virus spread to neighboring countries.

OBJECTIVES

As we approach the eradication of poliomyelitis, one of the global challenges is to control and interrupt the transmission of the vaccine-derived polioviruses. In Senegal, an outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2) of the NIE-JIS-1 emergence group was previously reported from 2020 to 2021.

METHODS

Our study report a newemergence of cVDPV2 in Senegal from 2023 to 2024, first detected in sewage and later in stool samples from children with acute flaccid paralysis, particularly, in Southeastern Senegal.

RESULTS

All recent strains from Senegal were genetically linked, and one sequence was linked to the type 2 novel oral polio vaccine. The phylodynamic analysis showed that the 2023-2024 cVDPV2 sequences from Senegal grouped into a monophyletic group with strains from the Republic of Guinea, and belonged to the NIE-ZAS-1 emergence group. Our data also show that the NIE-ZAS-1 virus was introduced to Senegal around 2010 (95% Highest Posterior Density, 2003-2017) and recently spread to the Republic of Guinea and the Republic of Mauritania in 2023 while it continuously circulated in Senegal between 2023 and 2024.

CONCLUSION

Our data highlight the importance of strengthening the poliovirus vaccine coverage and surveillance in these countries characterized by frequent population movements. Moreover, more studies on risks associated with VDPV2 mutations to enhance virulence are warranted.