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A SARS-CoV-2 mutation that appeared in East Asia early in the pandemic is linked to symptoms milder than those caused by the unmutated version of the virus. In early 2020, researchers in Singapore identified a cluster of COVID-19 cases caused by a SARS-CoV-2 variant missing a chunk of DNA that spanned two genes, ORF7b and ORF8. To determine the consequences of this change, called a deletion, Lisa Ng at the Singapore Immunology Network and colleagues compared people infected with viruses carrying the deletion with those infected by normal viruses (B. E. Young et al. Lancet http://doi.org/d6x7; 2020).
None of the 29 people whose viruses had the mutation needed supplemental oxygen, but 26 of the 92 people whose viruses lacked the mutation did. Viruses carrying the deletion haven’t been detected since March — possibly owing to infection-control measures. The virus responsible for the 2002–04 outbreak of severe acute respiratory syndrome (SARS) acquired a similar deletion in the ORF8 gene, suggesting that this might be an important adaption to infecting humans, the authors say.
Study published in The Lancet (August 18, 2020):
