Genomic epidemiology reveals early transmission of SARS-CoV-2 and mutational dynamics in Nanning, China (preprint)

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are a fatal pathogen resulting in substantial morbidity and mortality, and posing a great threat to human health with epidemics and pandemics. Methods: Next-generation sequencing (NGS) was performed to investigate the SARS-CoV-2 genomic characterization. Phylogenetic analysis of SARS-CoV-2 genomes was used to probe the evolutionary. Homology protein structure modelling was done to explore potential effect of the mutations. Results: The eighty genome sequences of SARS-CoV-2 obtained from the thirty-nine patients with COVID-19. A novel variant with mutation H625R concomitant with S50L in spike glycoprotein had been identified. Phylogenetic analysis revealed that SARS-CoV-2 variants belong to several distinct lineages. Homology modelling indicated that variant with mutation H625R and S50L increases flexibility of S1 subunit. Conclusions: SARS-CoV-2 genomes are constantly evolving by accumulation of point mutations. The amino acid H625R in combination with S50L may have a significant impact on the interaction between spike glycoprotein and ACE2.

An Imported Case of COVID-19 Delta Variant B.1.617.2---Guangxi Zhuang Autonomous Region, China, June 8, 2021 (preprint)

A male passenger arriving at Nanning Wuxu Airport in Guangxi on an international flight from Jakarta, Indonesia, was found to be positive for SARS-CoV-2 nucleic acid on a routine test at the airport on June 8 2021. The passenger was sent to Fourth People’s Hospital of Nanning immediately for further isolation and observation. On the day of admission, the test for SARS-CoV-2 nucleic acid of nasopharyngeal swabs, pharyngeal swabs and sputum specimens were positive (CT values of N gene and ORF1ab gene were between 20 and 30). After 8 weeks of hospitalization, the patient’s test for SARS-CoV-2 nucleic acid of all specimens turned to negative. We isolated a SARS-CoV-2 variant strain from the nasal swab of the patient, and then we found that the genome sequence of the variant strain had 13 base deletions and 38 nucleotide mutations compared with that of the Novel Coronavirus Wuhan strain after sequencing, comparison and analysis. The deletions and mutations of the variant strain resulted in four amino acid deletions and 30 amino acid mutations. Furthermore, we found that the variant strain was similar to those from Indonesia, South Korea and The United Kingdom after conducting BLAST analysis on GISAID platform, among them, hCOV-19 /Indonesia/ Ji-ITD-43591N /2021 was the most similar, with 99.98% similarity and only 8 base differences. The maximum likelihood phylogenetic tree was constructed taking the Wuhan strain as the root and including most the reference sequence contained most of the epidemic strains. The result showed that the strains isolated in our laboratory belonged to Delta strain.