Importation and Circulation of Vaccine-Derived Poliovirus Serotype 2, Senegal, 2020–2021
Martin Faye, Ousmane Kébé, Boly Diop, Ndack Ndiaye, Annick Dosseh, Abdoulaye Sam, Aliou Diallo, Hamet Dia, Jean Pierre Diallo, Ndongo Dia, Davy Kiori, Ousmane M. Diop, Amadou Alpha Sall, Ousmane Faye
Abstract
Environmental surveillance for poliovirus is increasingly used in poliovirus eradication efforts as a supplement to acute flaccid paralysis (AFP) surveillance. Environmental surveillance was officially established in 2017 in Senegal, where no poliovirus had been detected since 2010. We tested sewage samples from 2 sites in Dakar monthly for polioviruses. We identified a vaccine-derived poliovirus serotype 2 on January 19, 2021, from a sample collected on December 24, 2020; by December 31, 2021, we had detected 70 vaccine-derived poliovirus serotype 2 isolates circulating in 7 of 14 regions in Senegal. Sources included 18 AFP cases, 20 direct contacts, 17 contacts in the community, and 15 sewage samples. Phylogenetic analysis revealed the circulation of 2 clusters and provided evidence on the virus introduction from Guinea. Because novel oral polio vaccine serotype 2 was used for response activities throughout Senegal, we recommend expanding environmental surveillance into other regions.