The COVID-19 pandemic first emerged in Malaysia in Jan 2020. As of 12th Sept 2021, 1,979,698 COVID-19 cases that occurred over three major epidemic waves were confirmed. The virus contributing to the three epidemic waves has not been well-studied. We sequenced the genome of 22 SARS-CoV-2 strains detected in Malaysia during the second and the ongoing third wave of the COVID-19 epidemic. Detailed phylogenetic and genetic variation analyses of the SARS-CoV-2 isolate genomes were performed using these newly determined sequences and all other available sequences. Results from the analyses suggested multiple independent introductions of SARS-CoV-2 into Malaysia. A new B.1.524(G) lineage with S-D614G mutation was detected in Sabah, East Malaysia and Selangor, Peninsular Malaysia on 7th October 2020 and 14th October 2020, respectively. This new B.1.524(G) group was not the direct descendant of any of the previously detected lineages. The new B.1.524(G) carried a set of genetic variations, including A701V (position variant frequency = 0.0007) in Spike protein and a novel G114T mutation at the 5’UTR. The biological importance of the specific mutations remained unknown. The sequential appearance of the mutations, however, suggests that the spread of the new B.1.524(G) lineages likely begun in Sabah and then spread to Selangor. The findings presented here support the importance of SARS-CoV-2 full genome sequencing as a tool to establish an epidemiological link between cases or clusters of COVID-19 worldwide.
Various methods have been developed for rapid and high throughput full genome sequencing of SARS-CoV-2. Here, we described a protocol for targeted multiplex full genome sequencing of SARS-CoV-2 genomic RNA directly extracted from human nasopharyngeal swabs using the Ion Personal Genome Machine (PGM). This protocol involves concomitant amplification of 237 gene fragments encompassing the SARS-CoV-2 genome to increase the abundance and yield of viral specific sequencing reads. Five complete and one near-complete genome sequences of SARS-CoV-2 were generated with a single Ion PGM sequencing run. The sequence coverage analysis revealed two amplicons (positions 13751-13965 and 23941-24106), which consistently gave low sequencing read coverage in all isolates except 4Apr20-64-Hu. We analyzed the potential primer binding sites within these low covered regions and noted that the 4Apr20-64-Hu possess C at positions 13730 and 23929, whereas the other isolates possess T at these positions. The genetic variations observed suggest that the naturally occurring genome variations present in the actively circulating SARS-CoV-2 strains affected the performance of the target enrichment panel of the Ion AmpliSeq™ SARS‑CoV‑2 Research Panel. The possible impact of other genetic sequence variations warrants further investigation, and an improved version of the Ion AmpliSeq™ SARS‑CoV‑2 Research Panel, hence, should be considered.
The RT-PCR cycle threshold (Ct) value for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is inversely proportionate to the virus load in the patient’s specimen. These values could be beneficial to be used in monitoring the epidemic trajectory at the population level. The SARS-CoV-2 B.1.617.2 (Delta) variant which emerged in late 2020, caused an unprecedented exponential increase in SARS-CoV-2 infection cases worldwide. In Malaysia, the surge in coronavirus disease 2019 (COVID-19) cases and the inclining positivity rate contributed to the epidemic waves started in late May 2021. The sudden surge in cases was speculated to be associated with increased transmission caused by the emergence of the B.1.617.2 variant. This could be reflected by changes in the mean Ct value distribution which reflects the viral load in the population. In the present study, the Ct value distribution of COVID-19 infected person samples from the years 2020 and 2021 were tabulated against the SARS-CoV-2 genomic variants determined from genomic sequencing. A significant decreasing pattern of the mean Ct values from the overall 2020 and 2021 samples were noted (p<0.01). There was, however, high variability in the Ct values of samples obtained between 2020 and 2021 in contrast to samples with lower mean Ct value obtained in 2021. The percentages representation of SARS-CoV-2 genomic variants B.1.36 and B.1.524 were 31.6% and 68.4%, respectively, for samples obtained in October and December 2020. Whereas samples obtained in June and July 2021 were 100% of the B.1.617.2 variant. The decreasing trend in the Ct value distribution from samples tested in our laboratory correlated well with the increasing weekly COVID-19 cases reported by the Malaysia national data which was subsequently attributed by the emergence of B.1.617.2 in the country. This study suggests that the Ct value distribution of samples taken from the screening of SARS-CoV-2 infected population could provide insight into the potential epidemiologic transmission dynamic at the population level and when coupled to the virus genomic sequencing surveillance could allow detection of an emerging SARS-CoV-2 variant with different transmission behaviour. This could facilitate early response control strategies to limit the transmission of an emerging SARS-CoV-2 variant.
Various methods have been developed for rapid and high throughput full genome sequencing of SARS-CoV-2. Here, we described a protocol for targeted multiplex full genome sequencing of SARS-CoV-2 genomic RNA directly extracted from human nasopharyngeal swabs using the Ion Personal Genome Machine (PGM). This protocol involves concomitant amplification of 237 gene fragments encompassing the SARS-CoV-2 genome to increase the abundance and yield of viral specific sequencing reads. Five complete and one near-complete genome sequences of SARS-CoV-2 were generated with a single Ion PGM sequencing run. The sequence coverage analysis revealed two amplicons (positions 13 751-13 965 and 23 941-24 106), which consistently gave low sequencing read coverage in all isolates except 4Apr20-64-Hu. We analyzed the potential primer binding sites within these low covered regions and noted that the 4Apr20-64-Hu possess C at positions 13 730 and 23 929, whereas the other isolates possess T at these positions. The genome nucleotide variations observed suggest that the naturally occurring variations present in the actively circulating SARS-CoV-2 strains affected the performance of the target enrichment panel of the Ion AmpliSeq™ SARS CoV 2 Research Panel. The possible impact of other genome nucleotide variations warrants further investigation, and an improved version of the Ion AmpliSeq™ SARS CoV 2 Research Panel, hence, should be considered.
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