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(CNN) --
Arguably the most successful sub-variant of omicron to date has been the BA.2, but this one hasn't rested on its laurels.
The BA.2 subvariant has been churning out mutations, sometimes changing to versions that are fancier and, unbelievably, even faster than itself.
Global variant screeners have found 21 viral progeny associated with the omicron subvariant BA.2.
Most of these seem low yielding, with minor mutations.
But two of these offshoots, BA.2,12.1 and BA.2,12, have been driving a surge in Covid-19 cases and hospitalizations in central New York state.
And one of them, BA.2,12.1, is also outperforming BA.2 in other regions.
New data from the US Centers for Disease Control and Prevention (CDC) estimates that the BA.2,12.1 subvariant caused 19% of new covid-19 infections in the country last week, compared to to an estimated 11% of cases the week before and 7% last week and the week before this that.
The rate at which the BA.2,12.1 subvariant is outcompeting BA.2 is about as fast as BA.2 outperformed its cousin, BA.1, according to Trevor Bedford, an epidemiologist and genomics scientist at the College of Health. University of Washington Public.
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Although BA.2 is still around, it has lost some ground.
Last week, it caused about 74% of Covid-19 cases, according to CDC data, up from nearly 76% the week before.
Together, BA.2 and BA.2,12.1 accounted for about 93% of new COVID-19 cases in the US last week.
"BA.2,12.1 has increased rapidly in proportion in the US compared to other BA.2 sublineages," especially in the region that includes New York and New Jersey, CDC spokeswoman Kristen Nordlund said in an email. an email.
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Last week, the New York State Department of Health alerted residents to the new sublineages, warning that they were spreading about 25% faster than BA.2 and causing a surge in COVID-19 cases and hospitalizations, particularly in the central part of the state.
He urged New Yorkers to "act quickly" to consider wearing masks, receiving booster doses of vaccines, getting tested if they had symptoms and seeking treatment if infected.
Officials are concerned about the offshoots of BA.2 because they have swapped pieces of their spike proteins at key locations called L452Q and S704L.
Virologists have seen mutations at those positions before.
The Delta variant had a switch at 452, and this helped the virus bind more tightly to ACE2 receptors on our cells.
"And those mutations allow the virus to enter cells faster and also help evade antibody responses that are generated from vaccination or infection," said Andy Pekosz of the Johns Hopkins Bloomberg School of Public Health.
"What we really don't know at this point is how much those mutations are going to contribute to further spread or increased severity of the disease," he said.
"That's something that will take us some time to figure out."
Pekosz says he and others are working on it right now.
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That cases are increasing in New York is also a bit concerning.
It means that these viruses are good at overcoming our immune defenses.
"The vast majority of people in New York have either been vaccinated or infected or both. So what we're seeing are reinfections. We're seeing this immune evasion," said Dr. Daniel Griffin, a physician and researcher at New York Medical Center. Columbia University.
Two other subvariants of omicron, BA.4 and BA.5, have begun to circulate at low levels in other parts of the world, including South Africa, Botswana, Germany, and Denmark.
They also have mutations in 452, among others.
"I think it's interesting that we were moving towards a different kind of regimen for the evolution of SARS-CoV-2, where the virus can pick up mutations that are more transmissible, we've seen it at least three times now with omicron. So I think from a scientific standpoint, that's interesting," said Shishi Luo, associate director of bioinformatics and infectious diseases at Helix, a company that has been tracking variants of the coronavirus.
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Will the new subvariant affect public health?
What that might mean for public health remains an open question.
Luo says it's too early to know how well current COVID-19 vaccines defend against subvariants, but he's hopeful that because they're linked to BA.2, protection against serious outcomes like hospitalization and death will remain.
He notes that experts have not seen new subvariants increase Covid-19 hospitalizations in countries like South Africa.
So he is hopeful that even if cases start to rise here, hospitalizations will remain low.
If you've been previously vaccinated or infected, if your immune system has seen and recognized some of the viruses before, and you get Covid again, your chances of going to the hospital are reduced by about 90%, says Griffin.
If you test positive quickly enough and receive treatment, such as monoclonal antibodies or Paxlovid, the chance that you will end up in the hospital is reduced by 90%.
"If we do everything right from here on out, we shouldn't see a lot of people end up in the hospital," Griffin said.
He points out that getting covid is not yet free of risks.
From time to time you see people who ended up with prolonged covid after being vaccinated and having their booster dose.
"It's just a gamble. As long as people get infected, you still have a chance to get it despite vaccinations," Griffin said.
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