Five years after the COVID-19 pandemic began, the virus continues to spread around the globe as the virus continues to evolve. Scientists say that’s likely to continue indefinitely, as the virus finds new ways to evade the human immune system. At the moment, the virus has faded into the background of daily life even as people still get sick, end up in the hospital and sometimes die. But a new more dangerous variant could emerge at any time.
MARY LOUISE KELLY, HOST:
Five years after the pandemic erupted, COVID-19 has receded into the background for most people. But the virus behind the disease is still spreading widely and is still steadily mutating. NPR health correspondent Rob Stein brings us this look at the evolution of the deadly virus.
ROB STEIN, BYLINE: When the virus first emerged, many scientists thought this frightening new respiratory infection would evolve slowly, but that was one of the first big surprises from SARS-CoV-2. This virus, it evolved like crazy.
JESSE BLOOM: SARS-CoV-2, so far, has probably been even faster than influenza virus, which is really remarkable.
STEIN: Jesse Bloom studies viral evolution at the Fred Hutch (ph) Cancer Center in Seattle.
BLOOM: I thought it would undergo some evolution, but the speed at which it’s undergone that evolution and the ability it’s shown to undergo these big evolutionary jumps is really remarkable.
STEIN: Most notoriously, like when the virus made a huge evolutionary jump to spawn Omicron, which conquered the world with shocking speed. And that hasn’t changed. The virus has kept mutating, regularly begetting new variants.
BLOOM: It’s possible that the rate of evolution has slowed down a little bit, but the evolution of the virus has not stopped.
STEIN: But the menagerie of new mutants have pretty much all been descendants of Omicron, offspring that keep finding new ways to get around our immune systems. But something else has changed big time – the human immune system.
KRISTIAN ANDERSEN: As we got infected by the virus, but also really importantly, as we saw the vaccines roll out, that just build up immunity in the population, which means that SARS-CoV-2, all of a sudden, ran into this immunity wall.
STEIN: Kristian Andersen is an evolutionary biologist at the Scripps Research Institute in California.
ANDERSEN: And with the immunity wall, we have SARS-CoV-2 at least a little bit cornered now and is probably mostly in stasis by now because of that immunity wall.
STEIN: And it’s that immunity wall that keeps most people from getting very ill. Now, that doesn’t mean the virus isn’t a threat anymore. It hasn’t evolved to become inherently less dangerous, and it still makes lots of people sick. Sometimes so sick, they wind up in the hospital or even die. Hundreds perish every week in the U.S. from COVID, mostly older people and people with other health problems. But the virus has essentially become endemic, meaning this is the new normal. The virus is here to stay, but isn’t upending daily life anymore. Jeremy Kamil is an immunologist at the University of Pittsburgh.
JEREMY KAMIL: The immunity we built up, it makes it like trying to start a forest fire after a few weeks of heavy rain versus when everything’s tinder-dry.
STEIN: But the virus will keep evolving, trying to find new ways to sneak around our immunity wall. But most scientists think it isn’t likely to morph enough to cause more than mild illness for most people. Michael Worobey studies the evolution of viruses at the University of Arizona.
MICHAEL WOROBEY: We may just continue on in this phase of subvariants of subvariants of subvariants of Omicron – might just be what we deal with for decades and decades.
STEIN: With some years and some surges being better or worse than others, kind of like the flu, and with the chances being low that a much more dangerous new variant will suddenly erupt again. Experts stress, however, that’s not guaranteed. Jennifer Nuzzo of Brown University’s Pandemic Center says it’s crucial we maintain our immunity wall.
JENNIFER NUZZO: That wall of immunity is something that is built up over time, but it also can erode over time. And so to keep up that wall, we need to make sure we continue to protect ourselves.
STEIN: By getting vaccinated with updated vaccines once or twice a year to bolster waning immunity. Experts say that would help minimize the chances the virus would spread to someone, say, with a weak immune system, where the virus could simmer and mutate and make yet another dangerous evolutionary jump.
Rob Stein, NPR News.
Copyright © 2025 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
