'Pay attention to Omicron, worry more about Delta'

December 06, 2021
Blue virus particle shows original strain of coronavirus. Pink and purple version shows Delta. Red version shows Omicron.
A lot has changed since the original strain of the coronavirus that causes the illness COVID-19 emerged, including the arrival of variants. iStock

Every geographic area that the Medical University of South Carolina tracks has seen what a scientist called “significant increases” in COVID-19 cases as we head toward the winter holidays. “It’s not going in the right direction,” said Michael Sweat, Ph.D.

MUSC monitors COVID cases in the Charleston, Florence, Lancaster and Midlands areas, all of which have MUSC Health hospitals.

  • Charleston was up 43%, with 12 cases per day for every 100,000 people.
  • Florence was up 71%, with 17 cases per day for every 100,000 people.
  • Lancaster was up 39%, with 23 cases per day for every 100,000 people.
  • Midlands was up 65%, with 17 cases per day for every 100,000 people.

“This is totally Delta,” Sweat said, referring to the highly contagious coronavirus variant that accounts for virtually all COVID cases in the state right now. “There’s been a huge amount of concern in the press about Omicron, but right now we're facing a Delta threat and people have just largely given up on masking and distancing and other measures.”

The numbers are relatively small right now, so Sweat said this is not the time for alarm. “We're getting advance warning here. I think we need a couple more days.”

Dr. Michael Sweat 
Dr. Michael Sweat

One factor he’s watching closely is the basic reproduction number, also known as Rt. It shows the average number of people each infected person passes along the virus to. If the Rt is below one, that’s good news. “But we're getting some volatility above one, which tends to predict a wave coming,” Sweat said.

“When Rts are elevated before a peak in cases, it’s the time when mitigation efforts have the biggest effects. We’re getting close. But I don’t know that I would pull the trigger just yet on any kind of big changes. I'll watching those Rt values over the next few days to see if they’re going to stay above one. They may go back down a little.”

It’s a reminder that there are a lot of unknowns. For example, we know we have vaccines this winter, unlike last winter — but we also have the Delta variant, which we didn’t have last year. And we know only about half of all residents in South Carolina are fully vaccinated. 

But we don’t know what the newest variant, the fast-spreading Omicron, will do. While reports suggest it may be less dangerous than Delta, it’s early days, Sweat said.

“There's a lot of reasons I'd be cautious about the idea that Omicron might not be severe. One of them is looking at the virus mutations. A bunch of them in Omicron are associated with more severe outcomes and other variants. Two, there are reports in South Africa that hospitalizations are going up in a way that’s very similar to what Delta did. There's just so much uncertainty,” Sweat said.

“I did hear a report today that the amount of time people are staying in the hospital was only two-and-a-half days, as opposed to eight-and-a-half days for prior COVID infections. So that might suggest it's milder. But I don’t think we should assume it’s milder than Delta or worse than Delta. Right now, it’s just the fog of war.”

The war against the coronavirus, underway since winter of 2019, has had many murky moments for scientists and the public. Sweat, a professor in the College of Medicine who’s also affiliated with the Johns Hopkins Bloomberg School of Public Health and served as research scientist with the Centers for Disease Control and Prevention, said we should focus on what’s clear. His bottom line — and headline: “Pay attention to Omicron, worry more about Delta.”

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