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Science

Why omicron may cause less harm — and what it means for the future of the pandemic

MARY LOUISE KELLY, HOST:

After two years of the COVID pandemic, the U.S. is in the midst of what could be the worst surge yet in terms of cases. But there is still hope deaths will be lower with this surge than previous ones. Although many, many people are or will be infected, there are signs that SARS-CoV-2 has changed, that the omicron variant is less likely to cause severe disease. NPR's Michaeleen Doucleff looks into why that may be and what it means for the future of the pandemic.

MICHAELEEN DOUCLEFF, BYLINE: When doctors in South Africa started reporting that omicron could be less severe than delta, Ravi Gupta immediately wanted to figure out why.

RAVI GUPTA: We then very quickly started in the lab working omicron when we heard this.

DOUCLEFF: Gupta is a microbiologist at the University of Cambridge. He and his colleagues wanted to see if the virus had changed somehow, maybe in the way it infects cells, in a way that makes it less dangerous. He and his team ran a few experiments and immediately they saw that omicron was different than delta. It doesn't infect lung cells as well.

GUPTA: And that was a real shock because we were seeing a virus that was spreading very, very rapidly globally and yet was really attenuated in certain cell types.

DOUCLEFF: They also found that omicron uses a different path to enter cells than delta does, and this entryway likely causes less damage to lung cells.

GUPTA: And this, I think, is having quite marked consequences in terms of what we're seeing clinically - the lack of pneumonitis and sort of progression to requirement for oxygen that we were seeing in patients.

DOUCLEFF: Together, with data from hospitals and animal studies, these results offer strong evidence that omicron is somewhat less virulent than delta. But what does this less virulence mean for future surges? Dr. Ruby Bhattacharya at Harvard Medical School says right now there's this narrative in the media, on social media, maybe even at your dinner table, that omicron being less severe is a sign that the virus is weakening and evolving into a more mild illness.

RUBY BHATTACHARYA: You know, I think there's this story that we're going to get viruses that are progressively less severe.

DOUCLEFF: But that's completely untrue. That's a myth.

BHATTACHARYA: It's comforting to think there might be some tendency to evolve towards a milder form. That's not what we're seeing here.

DOUCLEFF: In fact, before omicron came along, SARS-CoV-2 was actually evolving to be more severe.

BHATTACHARYA: Delta was about two times as likely to put you in the hospital as alpha, which came before it.

DOUCLEFF: And Bhattacharya says there's no guarantee the variant that comes next will be as mild as omicron. It could be the worst one yet, cause the most severe illness. Why is that? Well, Bhattacharya says SARS-CoV-2 is spread at the beginning of the infection, even before people know they're sick. And that's when people are infected primarily in the upper respiratory tract. So to spread to more people, the virus has to become really good at upper respiratory tract infections. And it really doesn't matter what's going on in the lungs. So Bhattacharya says future variants will likely continue to be more infectious in the upper respiratory tract. But in terms of severity...

BHATTACHARYA: I think it's kind of luck of the draw whether that also makes it more severe or that also makes it less severe.

DOUCLEFF: Now, on the surface, this sounds kind of horrible, right? It suggests the next surge after omicron could be worse than even the delta surge. But there's one factor we need to take into account. There's something else that's changing besides the virus - people's immunity. More than half of the U.S. population has likely been infected. More than 60% are vaccinated. Stephen Goldstein at the University of Utah says both of those types of exposures will reduce a person's risk of severe disease in future surges, and thus will end up making any future variant look less severe and less deadly.

STEPHEN GOLDSTEIN: Even if you had a virus that had no change in virulence, if the population is now - has a high level of existing immunity, then it will, in effect, be less virulent because the average severity of infections will go down over time.

DOUCLEFF: And so the hope is, no matter what the virus throws at us, over time, future waves of COVID will be less deadly and less disruptive because our bodies are better able to handle it, not because the virus has changed itself.

Michaeleen Doucleff, NPR News. Transcript provided by NPR, Copyright NPR.