Immersed in a second wave and with the most likely following outbreaks on a not-so-distant horizon, scientists around the world study the behavior of SARS-CoV-2 coronavirus to try to tackle its spread around the world even before a vaccine arrives. The U.S. city of Houston, with a population of more than 7 million people, is experiencing a massive spike in contagion that began in late May 2020. In response, the University of Texas at Austin has conducted a study of more than 5,000 covid-19 patients to “understand the architecture and genomic evolution of the molecular population of the virus and the relationship between the virus genotypes and patient characteristics.” Thus, they have discovered that the disease is accumulating genetic mutations and one of which may have made it more contagious.
According to the article published in the journal mBIO, that mutation, called D614G, is found in the spike protein that opens our cells for viral entry. The document shows that “the virus is mutating due to a combination of neutral drift, which only means random genetic changes that do not help or harm the virus, and pressure from our immune system,” says Ilya Finkelstein, associate professor of molecular biosciences at the University of Texas and a co-author of the study.
During the initial wave of the pandemic, 71% of the new coronavirus infections identified in patients in Houston had this mutation. When the second wave began during the summer, the variant had increased to 99.9% prevalence. These results reflect the trend demonstrated in another report published in July and based on more than 28,000 genome sequences and in which it was found that variants carrying the D614G mutation became the dominant strain in about a month and worldwide.
Experts now wonder why the strains containing this mutation outnumbered those without it. While a study of more than 25,000 genome sequences in the UK found that viruses with the D614G mutation tend to spread a little faster than those without it, another group of scientists believe it would be “the founder effect”. That is, this strain could have been more common in the first cases that reached Europe and North America, giving it an advantage over other strains.
Variants carrying the D614G mutation became the dominant strain in about a month and worldwide
“The virus continues to mutate as it sweeps the world,” says Finkelstein, adding: “Real-time surveillance efforts like our study will ensure that global vaccines and treatments are always one step ahead.”
Scientists have also observed a total of 285 mutations in thousands of types of infections, although most do not appear to have a significant effect on the severity of the disease in patients. However, ongoing studies continue to work to discover how the virus is adapting to the neutralizing antibodies that are produced by our immune system to try to understand why each body reacts so differently to the spread of the same virus such as covid-19.
The Houston team has also shown that at least one of those mutations allows the spike to bypass a neutralizing antibody that humans produce naturally to fight SARS-CoV-2 infections. This could cause that strain of virus to more easily ‘escape’ from our immune system.