A new study has identified small mutations in genes of early COVID-19 viruses that appeared to have substantially increased the risk of severe disease in patients who contracted them.
The researchers, who carried out extensive, whole-genome sequencing of the viruses taken from patients primarily in the first year of the pandemic, spotted in particular a group of four genetic mutations that were linked to a 5.46-fold increase in hospitalization.
“5.46 is a large effect,” said Dr. Lue Ping Zhao, a biostatistician at Fred Hutchinson Cancer Research Center, who is the lead author of a paper on the study published online by the journal Scientific Reports on Jan. 24.
While much of coronavirus research focuses on ways to block transmission, this study sought to identify virulence factors — traits that would make the virus cause more serious illness. To do so, it sequenced every viral genome from virus samples taken from 683 patients from Washington state. Roughly half the patients were so sick they were hospitalized, while the rest were treated in a medical office setting.
When the scientists analyzed the genomic data, one particular set of mutations stood out among the hospitalized patients — just four letters in the genetic code that differed from that of the most common reference strains of the virus. It was identified by the four changed letters: caac.
