Dominant COVID mutant in US combines elements of Omicron and Delta, complicating response

The mutant coronavirus now dominant in the United States is a member of the Omicron family, but scientists say it spreads faster than its Omicron predecessors, is adept at escaping immunity, and could potentially cause more serious diseases .

Why? Because it combines characteristics of Omicron and Delta, the country’s dominant variant in the middle of last year.

A genetic trait dating back to the pandemic’s past, known as the “delta mutation,” appears to allow the virus to “escape pre-existing immunity from vaccination and previous infections, especially if you got infected in the Omicron wave.” said Dr Wesley Long, pathologist at Houston Methodist in Texas. That’s because the original Omicron tribe that took over the world didn’t have this mutation.

The Omicron “subvariant” gaining ground in the US — known as BA.2.12.1 and responsible for 58% of US COVID-19 cases last week — isn’t the only one affected by the delta mutation is. The genetic alteration is also present in the Omicron relatives collectively dominant in South Africa, known as BA.4 and BA.5. These have the exact same mutation as Delta, while BA.2.12.1 has an almost identical one.

This genetic change is bad news for people who caught the original omicron and thought they were unlikely to get COVID-19 again anytime soon. Although most people don’t know exactly which variant caused their disease, the original Omicron caused a huge surge of cases late last year and early this year.

Long said laboratory data suggest that prior infection with the original omicron is not very protective from reinfection with the new mutants, although the true risk of reinfection is unique to each person and situation, regardless of variant.

However, in a twist, those previously ill from Delta can have additional armor to ward off the new mutants. A study, published before it was reviewed by other scientists, by Ohio State University researchers, found that COVID patients in the ICU with delta infections induced antibodies that were better at neutralizing the new mutants than patients who had the original Omicron caught.

“The Omicron infection antibody does not appear to provide good protection against the subvariants compared to Delta,” said Dr. Shan-Lu Liu, study author who co-directs Ohio State’s Virus and Emerging Pathogens Program.

But Liu said the level of protection that Delta infection offers depends in part on how long someone has been sick. This is because immunity wears off over time.

People who have delta should not consider themselves invulnerable to the new subvariants, especially if they are unvaccinated, Long said. “I wouldn’t say anyone is safe.”

A glimpse of hope? Booster shots can provide strong protection against the new mutants, Liu said. In general, vaccines and prior infections can protect people from the worst of COVID-19. Scientists say it’s too early to know at this point if the new mutant gaining ground in the US will cause a significant spike in new cases, hospitalizations and deaths.

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Scientists are still trying to figure out how virulent these new mutants are. Long said he didn’t see anything that answers that question for him, but Liu said emerging data points to a more serious disease. Liu said the subvariants have characteristics that suggest they spread from cell to cell more efficiently.

The virus “simply hides in the cell and spreads through cell-to-cell contact,” Liu said. “That’s scarier because the virus doesn’t come out for the antibody to work.”

dr Eric Topol, head of the Scripps Research Translational Institute, said the new mutants certainly appear to be no less virulent than previous versions of Omicron, and whether or not they are more virulent “will become clear in the coming months.”

Meanwhile, scientists expect the latest powerhouse mutants to spread quickly because they are more transmissible than their predecessors.

Though home testing makes it difficult to track all US COVID cases, data from Johns Hopkins University shows the number of cases is averaging nearly 107,000 a day, up from about 87,000 two weeks ago. And new hospital admissions for patients with COVID-19 have been trending upwards since around mid-April, according to the Centers for Disease Control and Prevention.

“I’m confident that we’re not seeing a surge in hospitalizations similar to what we’ve seen in previous waves,” Long said. “But with COVID, any time a lot of people are infected, it’s just a numbers game. Some of these people will be strict. Some of these people need to be hospitalized. Unfortunately, some of them will die.”

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