If there’s one thing we’ve learned from the pandemic, it’s that evolution isn’t necessarily a lengthy process that takes thousands, if not millions, of years.
It can be rapid and ruthless.
On Tuesday the U.S. Centers for Disease Control and Prevention announced that new(ish) Omicron subvariant BA.5, which swept South Africa this spring, had finally become dominant in the U.S. after first being detected there in March.
But there was no chance for the subvariant to celebrate, were it able to. On the same day, the World Health Organization tweeted a video about a new concerning variant surging in India—one giving BA.5, the most highly transmissible, immune-evasive version of COVID yet, a run for its money.
BA.2.75—dubbed “Centaurus” by some on Twitter—has already arrived in the U.S., the CDC told Fortune on Thursday, with the first of two cases identified on June 14.
It’s been located in approximately 10 countries so far, Dr. Soumya Swaminathan, WHO’s chief scientist, said this week. It’s not yet been declared a variant of concern or even a variant of interest, and it’s too soon to gauge transmissibility, severity, and the potential for immune evasion, she added.
But some experts are already raising red flags—particularly the additional changes (as many as nine) it has when compared to Omicron.
No one change is individually concerning, “but appearing all together at once is another matter,” Tom Peacock, a virologist at the Department of Infectious Disease at Imperial College in London, said this week in a tweet.
BA.2.75 is “something we should all be concerned about,” Dr. Bruce Walker—director of the Ragon Institute of MGH, MIT, and Harvard, a medical institute focused on eradicating disease, and co-leader of the Massachusetts Consortium on Pathogen Readiness—told Fortune on Friday.
The nascent variant “gives us insight into just what the virus is capable of, in terms of mutation. Here again is a virus that has resemblance to the original Omicron variant, but with minor amino acid changes has become something that is likely to be able to evade immunity.”
“I think what all of these variants are showing us is that the virus has not come anywhere close to exploring all of the evolutionary space available to it.”
A blip on the radar or a new global wave?
Whether BA.2.75 will cause a global wave or quickly fizzle—as did variants Lambda and Mu—remains to be seen, said Dr. Stuart Ray, vice chair of medicine for data integrity and analytics and a professor at Johns Hopkins Medicine.
“There are variants that we see sporadically pop up and have features that make us worry,” he said. “But until we see them out-compete in multiple settings, it’s hard to know what they’re going to mean for us.”
Such variants once flew under the radar but are now gaining attention as a result of “heightened surveillance and increased attention to sequencing,” said Dr. Daniel Kuritzkes, chief of the division of infectious diseases at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School.
“We’ve seen all kinds of variants within the Omicron family,” Kuritzkes said. “We really need to see a substantial number of cases rising in many locations to know that it’s truly a major variant of concern.”
Some of BA.2.75’s mutations are worrisome, and “some we don’t know much about,” Dr. Dan Barouch—a professor of medicine at Harvard Medical School and the director of the Center for Virology and Vaccine Research—told Fortune.
“It’s a reason to study it, but not a reason for panic,” he said.
‘Bad Ned’ and relatives emerge
“Centaurus” wasn’t the only COVID subvariant to catch eyeballs this week. The twitterverse—where many doctors, researchers, and data scientists post lengthy threads on COVID-related findings—also saw chatter about BA.5.3.1, aka “Bad Ned.”
The name is symbolic of its mutation on N:E136D, according to Australian data visualist Mike Honey, the author of a popular thread on the topic this week.
Bad Ned is a spin-off of the BA.5 subvariant currently sweeping the globe. In Germany, where it’s been on the rise since late May, it’s responsible for nearly 80% of BA.5 cases, according to Honey.
BA.5.3.1 has also been identified in the U.S., a CDC spokesperson told Fortune on Thursday. But it represents less than 5% of BA.5 cases in the U.S., he said.
Another BA.5 relative that hit radars this week: BA.5.1, which is increasing in prevalence in the U.K., Barouch said.
“The variants and subvariants are fragmenting quickly,” he said. “There’s not one or two, but hundreds of variants and subvariants.”
Is Omicron COVID’s ‘sweet spot’?
Omicron burst on the scene in early November 2021. Nothing—and everything—has been the same since.
Kuritzkes finds it interesting that every successful variant (or subvariant, rather) since has been an Omicron spinoff: “stealth Omicron” BA.2, BA.2 spinoff BA.2.12.1, BA.4, BA.5.
“We continue to see derivatives of Omicron rather than something completely different emerging,” he said. “Before Omicron, everything that came up was very different from what had been circulating. Delta didn’t come from Beta; Beta didn’t come from Alpha.”
“The virus may have finally found an evolutionary niche where this is the best it can do, and it’s modifying, tinkering around the margins to gain slight advantages.”
Some point to Omicron’s supposedly more mild symptoms and apparent predilection for the upper respiratory tract as compared to the original strain, which often settled in the lower lungs, posing greater risk for pneumonia and death.
Less severe disease and higher transmissibility could actually be a good thing, some contend, if it means Omicron is fizzling to nothing more than a cold, albeit a rampant one.
But it’s too early to come to that conclusion, Kuritzkes said.
Prior COVID infection is common, as is vaccination. Population immunity could be deceiving, making Omicron appear generally milder than it would in its absence.
Kuritzkes points to a BA.2 outbreak in Hong Kong several months ago that ravaged older generations.
“The elderly population was relatively unvaccinated,” he said. “There was very high mortality. That undermines the concept that Omicron is not as virulent as the others.”
Time will tell whether emerging subvariants are viable threats or mere distractions.
But if you come down with a weird summer cold—or worse—COVID could be to blame. If it’s not BA.5 or Centaurus or Bad Ned, it’s likely some other new-fangled Omicron spawn.
The possibilities are endless.
Said Walker: “There are an infinite number of combinations of mutations that can arise that can affect transmissibility and immunity.”
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