Scientists in Houston on Wednesday released a study of more than 5,000 genetic sequences of the coronavirus, which reveals the virus’s continual accumulation of mutations, one of which may have made it more contagious.

That mutation is associated with a higher viral load among patients upon initial diagnosis, the researchers found.

The study, which has not been peer-reviewed, was posted Wednesday on the preprint server MedRxiv. It appears to be the largest single aggregation of genetic sequences of the virus in the United States thus far. A larger batch of sequences was published earlier this month by scientists in the United Kingdom, and, like the Houston study, concluded that a mutation that changes the structure of the “spike protein” on the surface of the virus may be driving the outsized spread of that particular strain.

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The tiny mutation found in the dominant

coronavirus variant

Like all coronaviruses, SARS-CoV-2 has a series of characteristic spikes surrounding its core. These spikes are what allow the virus to attach to human cells.

SPIKE

Spike

SARS-CoV-2

Amino acid 614

A mutation affecting the spike protein changed amino acid 614 from “D” (aspartic acid) to “G” (glycine). Research suggests that this small change — which affects three identical amino acid chains — might enhance the virus’s transmissibility.

Source: Global Initiative on Sharing All Influenza Data

The new report, however, did not find that these mutations have made the virus deadlier. All viruses accumulate genetic mutations, and most are insignificant, scientists say. Coronaviruses such as SARS-CoV-2 are relatively stable as viruses go, because they have a proofreading mechanism as they replicate.

But every mutation is a roll of the dice, and with transmission so widespread in the United States — which continues to see tens of thousands of new, confirmed infections daily — the virus has had abundant opportunities to change, potentially with troublesome consequences, said study author James Musser of Houston Methodist Hospital.

“We have given this virus a lot of chances,” Musser told The Washington Post. “There is a huge population size out there right now.”

Scientists from Weill Cornell Medicine, the University of Chicago, Argonne National Laboratory and the University of Texas at Austin also contributed to the study.

David Morens, a virologist at the National Institute of Allergy and Infectious Diseases, reviewed the new study and said the findings point to the strong possibility that the virus, as it has moved through the population, has become more transmissible, and that this “may have implications for our ability to control it.”

Morens noted that this is a single paper, and “you don’t want to over-interpret what this means.” But the virus, he said, could potentially be responding — through random mutations — to such interventions as mask-wearing and social distancing, Morens said Wednesday.

“Wearing masks, washing our hands, all those things are barriers to transmissibility, or contagion, but as the virus becomes more contagious it statistically is better at getting around those barriers,” said Morens, senior adviser to Anthony S. Fauci, the director of NIAID.

This has implications for the formulation of vaccines, he said. As people gain immunity, either through infections or a vaccine, the virus could be under selective pressure to evade the human immune response.

“Although we don’t know yet, it is well within the realm of possibility that this coronavirus, when our population-level immunity gets high enough, this coronavirus will find a way to get around our immunity,” Morens said. “If that happened, we’d be in the same situation as with flu. We’ll have to chase the virus and, as it mutates, we’ll have to tinker with our vaccine.”

At Houston Methodist, whose main hospital is part of the Texas Medical Center in central Houston but also includes hospitals around the city, scientists have been sequencing the 30,000-character genome of the coronavirus since early March, when the virus first appears to have arrived in the metropolitan area of 7 million. The paper documents 5,085 sequences.

The research shows that the virus disseminated across Houston neighborhoods in two waves, first striking wealthier and older individuals but then spreading, in the second wave, to younger people and lower income neighborhoods — affecting many Latino city residents.

At the same time, as the virus spread Zip code by Zip code, it also compiled a catalogue of mutations, many affecting the spike protein. That structure on the surface of the virus, which resembles a tree decked with curled ribbons, enables the virus to enter cells. . Read more at Washington Post