Genetic Diversity of Norovirus in Children with Acute Gastroenteritis in Southwest Nigeria, 2015–2017

Norovirus (NoV) is a leading cause of viral gastroenteritis globally, especially in children below five years. Epidemiological studies on the diversity of NoV in middle- and low-income countries, including Nigeria, are limited. This study aimed to determine the genetic diversity of NoV in children below five years with acute gastroenteritis at three hospitals in Ogun State, Nigeria. A total of 331 fecal samples were collected from February 2015 to April 2017, while 175 were randomly selected and analyzed using RT-PCR, partial sequencing and phylogenetic analyses of both the polymerase (RdRp) and capsid (VP1) genes. NoV was detected in 5.1% (9/175; RdRp) and 2.3% (4/175; VP1) of samples, with 55.6% (5/9) co-infection with other enteric viruses. A diverse genotype distribution was identified, and GII.P4 was the dominant RdRp genotype detected (66.7%), with two genetic clusters, followed by GII.P31 (22.2%). The rare GII.P30 genotype (11.1%) was detected at a low rate for the first time in Nigeria. Based on the VP1 gene, GII.4 was the dominant genotype (75%), with two variants, Sydney 2012 and possibly New Orleans 2009, co-circulating during the study. Interestingly, both intergenotypic, GII.12(P4) and GII.4 New Orleans(P31), and intra-genotypic, GII.4 Sydney(P4) and GII.4 New Orleans(P4), putative recombinant strains were observed. This finding suggests the first likely report of GII.4 New Orleans(P31) in Nigeria. In addition, GII.12(P4) was first described in Africa and globally in this study, to the best of our knowledge. This study provided insights into the genetic diversity of NoV circulating in Nigeria, which would be useful for ongoing and future vaccine design and monitoring of emerging genotypes and recombinant strains.