SALT LAKE CITY — The COVID-19 virus continues to mutate, with a pair of new highly transmissible omicron subvariants sending cases spiking in South Africa.

It's not clear whether the new subvariants, dubbed BA.4 and BA.5 by scientists and responsible for tripling the virus caseload in South Africa, cause milder or more severe illness or if they're going to surge in other parts of the world, The New York Times reported.

So far, neither subvariant has been detected in Utah, according to Kelly Oakeson, the Utah Department of Health's chief scientist for next generation sequencing and bioinformatics, although they're starting to show up in Europe, which has already seen recent surges driven by other versions of the virus.

"We're watching evolution in process here, in real time," Oakeson said.

He said the state lab should have a new report on which versions of the virus are in Utah by the end of the week, after halting genome sequencing of test samples over the past two weeks for equipment maintenance. The lab, which processed up to 4,500 test samples a week at the height of the last outbreak, now gets only a few hundred weekly.

A new study cited in the Washington Post concluded the subvariants have the "potential to result in a new infection wave," because they're evading the neutralizing antibodies in people previously infected with the original omicron variant first seen in South Africa last November and responsible for last winter's skyrocketing cases in Utah.

The subvariants are raising new concerns about what's next with COVID-19.

"The evolution is much more rapid and expansive than we initially estimated," Michael T. Osterholm, a University of Minnesota infectious-disease expert, told The Washington Post. "Every day I wake up, I fear there will be a new subvariant that we will have to consider. … We're seeing subvariants of subvariants."

Oakeson said there's nothing stopping the virus from becoming more dangerous as it mutates.

He said while the latest subvariants appear to be even better at infecting people than previous versions, even those who are up to date on their vaccinations and booster shots or who've already had COVID-19, it remains to be seen if they're making people sicker.

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COVID-19 cases are climbing again in much of Europe and Asia, including in China, where the largest surge since the virus first emerged from that country more than two years ago has resulted in several large factory cities being locked down.

"It's still too early on to tell what clinical outcomes are going to be," Oakeson said, adding, "With viruses, there is no rule that says over time, they evolve to be less severe. ... That just doesn't happen. Natural selection, evolution, is random. So those mutations that happen as the virus replicates happen randomly."

That means, he said, "most of the time, a lot of those changes have no effect at all. They don't hurt or harm the virus, they're just there. But then there are the ones that happen to make it more transmissible, like we're seeing with omicron BA.4 and BA.5," along with the possibility of more severe outcomes.

Currently, an earlier omicron subvariant, known as BA.2 to scientists but also called "stealth omicron," dominates in the United States, estimated to be the cause of more than 68% of all cases, according to the Centers for Disease Control and Prevention.

But one of the subvariants of BA.2 — labeled BA.2.12.1 — accounts for nearly 29% of U.S. cases. In the region that includes Utah, the CDC estimates 76.5% of cases are from "stealth omicron," while 17% are the result of the BA.2.12.1 subvariant.

While the state is focused on keeping an eye out for the newest subvariants, Oakeson said there are larger discussions underway about what's coming next.

"Are we going to kind of keep seeing this drift in refinement of omicron sublineages, to get better and better and better at being transmissible and infectious? Or do we see something that pops up that's totally new, like omicron was?" he said.

There's no easy answer.

"It's still kind of some debate about what's going to happen," Oakeson said. "It's hard to say. We really don't have a good idea. ... The best we can do is keep our surveillance systems in place and up and running and catch them as they arrive and respond appropriately."

Cases are starting to climb again in Utah, according to the state health department's now-weekly update on the spread of the virus. Under Gov. Spencer Cox's "steady state" pandemic response that took effect last month, the state is treating COVID-19 more like the flu or other deadly but more predictable disease.

Oakeson said trying to keep the variants, subvariants — and subvariants of subvariants — straight is confusing. He advised Utahns to continue to protect themselves and others by getting vaccinated and boosted, social distancing and wearing a mask in crowded places.

"Keep doing all those public health things we keep telling you to do," Oakeson said, and remember that those around you could be more vulnerable to the virus because of their age or medical condition. "Just keep doing it. I know it's annoying. It's frustrating. But it makes sense."

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