Importation and Circulation of Vaccine-Derived Poliovirus Serotype 2, Senegal, 2020-2021.

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.

National Surveillance of Acute Flaccid Paralysis Cases in Senegal during 2017 Uncovers the Circulation of Enterovirus Species A, B and C.

Polioviruses have been eliminated in many countries; however, the number of acute flaccid paralysis cases has not decreased. Non-polio enteroviruses are passively monitored as part of the polio surveillance program. Previous studies have shown that some enteroviruses do not grow in conventional cell lines used for the isolation of poliovirus according to the WHO guidelines. In order to evaluate the presence of enteroviruses, real-time RT-PCR was performed on Human Rhabdomyosarcoma (RD)-positive and RD-negative stool samples. A total of 310 stool samples, collected from children under the age of 15 years with acute flaccid paralysis in Senegal in 2017, were screened using cell culture and real-time RT-PCR methods. The selected isolates were further characterized using Sanger sequencing and a phylogenetic tree was inferred based on VP1 sequences. Out of the 310 stool samples tested, 89 were positive in real-time RT-PCR. A total of 40 partial VP1 sequences were obtained and the classification analysis showed that 3 (13%), 19 (82.6%), and 1 (4.4%) sequences from 23 RD-positive non-polio enterovirus isolates and 3 (17.6%), 7 (41.1%), and 7 (41.1%) sequences from 17 RD-negative stool samples belonged to the species EV-A, B, and C, respectively. Interestingly, the EV-B sequences from RD-negative stool samples were grouped into three separate phylogenetic clusters. Our data exhibited also a high prevalence of the EV-C species in RD-negative stool samples. An active country-wide surveillance program of non-polio enteroviruses based on direct RT-PCR coupled with sequencing could be important not only for the rapid identification of the involved emergence or re-emergence enteroviruses, but also for the assessment of AFP's severity associated with non-polio enteroviruses detected in Senegal.

Prevalence and Genetic Diversity of Aichi Virus 1 from Urban Wastewater in Senegal.

Aichi virus 1 (AiV-1) has been proposed as a causative agent of human gastroenteritis. In this study, raw, decanted, and treated wastewater samples from a wastewater treatment plant in an urban area of Dakar, Senegal, were collected. AiV-1 was detected in raw (70%, 14/20), decanted (68.4%, 13/19), and treated (59.3%, 16/27) samples, revealing a noticeable resistance of AiV-1 to chlorine-based treatment. Phylogenetic analysis revealed that all sequences clustered within genotype B. Our study presents the first report on the detection of AiV-1 in the environment of Dakar and constitutes indirect evidence of virus circulation in the population.