The results of this study showed that the presence of EVs and consequently EV-Cs in AFP samples declared to be EV-free by the RD-L20B cell culture-based algorithm varies by geographical region in Nigeria.

We recently showed that Enteroviruses (EVs); majorly species Cs (EV-Cs) were present in about 46.7% of faecal samples from children <15 years old diagnosed with Acute Flaccid Paralysis (AFP) in Nigeria but declared to be EV free by the RD-L20B cell culture based algorithm. In this study, we investigated whether this observed preponderance of EVs (and EV-Cs) in such samples vary by geographical region.In all, 108 samples (i.e. 54 paired stool suspensions from 54 AFP cases) previously confirmed negative for EVs by the WHO recommended RD-L20B cell culture based algorithm were analyzed in this study. The 108 samples were made into 54 pools (27 each from Northwest [NW] and Southsouth [SS] Nigeria). All samples were subjected to RNA extraction, cDNA synthesis and the WHO recommended seminestedPCR (snPCR) assay and its modifications. All amplicons were sequenced, and enteroviruses identified using the enterovirus genotyping tool and phylogenetic analysis.Altogether, EVs were detected in 16 (29.63%) of the 54 samples screened but successfully identified in 14 (25.93%): 10 from NW-and 4 from SS-Nigeria. Precisely, one (7.14%), two (14.29%) and 11 (78.57%) of the strains detected were EV-A, EV-B and EV-C respectively. The 10 strains from NW-Nigeria are 7 EV types and include CV-A10, E29, CV-A13, CV-A17, CV-A19, CV-A24 and EV-C99. The four EV types recovered from SS-Nigeria include E31, CV-A1, EV-C99 and EV-C116. EV-C99 is the only EV type that was detected in both NW-and SSNigeria.The results of this study showed that the preponderance of EVs and consequently EV-Cs in AFP samples declared to be EV free by the RD-L20B cell culture based algorithm vary by geographical region in Nigeria. It further confirmed the EV-B bias of the RD-L20B cell culture based algorithm.