Genetic analysis of SARS-CoV-2 strains collected from North Africa: viral origins and mutational spectrum

In Morocco two waves of SARS-CoV-2 infections have been recorded. The first one occurred from March 02, 2020 with infections mostly imported from Europe and the second one dominated by local infections. At the time of writing, the genetic diversity of Moroccan isolates of SARS-CoV-2 has not yet been reported.

The present study aimed to analyze first the genomic variation of the twenty-eight Moroccan strains of SARS-CoV-2 isolated from March 03, 2020 to May 15, 2020, to compare their distributions with twelve other viral genomes from North Africa as well as to identify their possible sources.

Our finding revealed 61 mutations in the Moroccan genomes of SARS-CoV-2 compared to the reference sequence Wuhan-Hu-1/2019, of them 23 (37.7%) were present in two or more genomes. Focusing on non-synonymous mutations, 29 (47.54%) were distributed in five genes (ORF1ab, spike, membrane, nucleocapsid and ORF3a) with variable frequencies. The non-structural protein coding regions nsp3-Multi domain and nsp12-RdRp of the ORF1ab gene harbored more mutations, with six for each. The comparison of genetic variants of fourty North African strains revealed that two non-synonymous mutations D614G (in spike) and Q57H (in ORF3a) were common in four countries (Morocco, Tunisia, Algeria and Egypt), with a prevalence of 92.5% (n = 37) and 42.5% (n = 17), respectively, of the total genomes. Phylogenetic analysis showed that the Moroccan SARS-CoV-2 strains were closely related to those from different origins (Africa, Asia, Europe, North and South America) and distributed in different distinct subclades. This could indicate different sources of infection with no specific strain dominating yet in Morocco.

These results have the potential to lead to new comprehensive investigations combining genomic data, epidemiological information and the clinical characteristics of patients with SARS-CoV-2.