As it races around the world, the COVID-19 omicron version shows tantalizing signs that it may be morphing into the ideal virus: highly transmissible, to be sure, but vaccines and milder than previous, sometimes lethal versions. nominated by.
Yet the evolutionary arms race between humans and viruses is not over, biologists say. This new relationship could be for the better – or it could suddenly get worse.
“We’re still in the early days of the ‘getting to know you’ phase,” said Stanford microbiologist Dr. David Railman. “And it is at this stage that things are least predictable, least well understood and most dynamic.”
“The virus will continue to try a lot of things,” he said, “because that’s how they succeed.”
If you are a virus, your only goal is to make more of yourself. You don’t care how many people you kill – or cause discomfort with only a mild case of sniffles. There is no advantage or disadvantage of causing COVID in the long run.
In the early days of the pandemic, what mattered for the virus was rapid transmission. But now it is facing a different scenario. We are getting used to, and soon we will all have vaccines or protective antibodies from infections.
“The virus initially has to learn to navigate a different immune environment,” said Jeremy Kamil, a virologist at the Louisiana State University Health Sciences Center Shreveport. “We are well equipped to fight these things. But from time to time, viruses come with retribution.”
Omicron conquered the Delta—another fast-spreading and most prevalent variant—because it spreads so quickly. While Delta settles in the lungs, Omicron supports the upper airway, where it can excrete copies of itself while talking and breathing. Its incubation period is only three days, compared to 4.3 days for Delta and five days for other types. It is more likely to be asymptomatic than other types; Instead of lying in bed, infected people feel fine or only slightly ill and spread it.
“One of the primary selective pressures on the virus for the past two years has been: ‘How do I reach as many people as possible as quickly as possible?’ Patrick Sq, an applied epidemiologist at the Chan Zuckerberg Biohub in San Francisco. “‘I can expect from anyone and have a great time.’ ,
Fortunately for humans, an omicron infection means less severe disease. Two new studies show that Omicron does not cling to lung cells as tightly or quickly, and is therefore less likely to cause pneumonia. Instead, it gives priority to an airway called the bronchus.
In its early days, this strategy worked for Edition, and it ran rampant. But that is now beginning to change – and will force the virus to attempt to revise its approach.
It is because we are changing too. In much of the world, the majority of the population has been infected or has had some form of vaccination, and some have immunity.
In the US, experts predict that if we follow the trends seen in South Africa, Denmark and the United Kingdom, January will see a sharp drop in omicron cases starting from the third or fourth week. By mid-February, Omicron will decrease. But that’s not necessarily a reason to celebrate.
“Omicron will run out to infect people,” Askew said. “It could give an opportunity for something else to come.”
When can this happen? Change can come about gradually through the accumulation of mutations. Or it could happen suddenly, as we saw at Omicron. A dramatic genetic variation is most likely if the virus grows in an immunocompromised individual, in wildlife, or if the two types mix together to form a super-hybrid.
“There is a very plausible scenario where the next could be worse. And there is a very plausible scenario where the next one might be better,” Andrew F. Reid, director of the Huck Institutes of Life Sciences at Penn State, which studies infectious disease development.
There are many worrying possibilities.
The COVID-19 virus may try to become more latent, like tuberculosis or HIV, with a long “silent” phase of infection, noted Kamil and Railman.
Or it could be something even more contagious, like measles, read noted. A virus that causes a severe cough will spread quickly – and while it will leave people safe, it can be fatal to anyone who lacks antibodies.
Could the next version be more lethal? This has happened with other viruses. For example, a herpes virus that afflicts chickens, called Marek’s disease, has been getting more severe since the 1970s, he said. And a deadly virus used to control rabbit populations in Australia has faded over time – but now, in a surprising twist, it is killing again.
“If another variant comes out that is transmissible and a little better at infecting the lungs, we will be back where we were with the delta version,” said Dr. Stanley Perlman, professor of microbiology and immunology at the University of Iowa. , But it is not inevitable; From the point of view of the virus, it does not matter whether we live or die.
The next winning version will be the one that’s most agile at dodging our immune defenses, experts agree.
But it will encounter a smarter human immune system that is also adaptable, and better trained to defend itself. And there are parts of the immune response, such as virus-killing T cells, that will target all types, said Bette Korber of the Los Alamos National Laboratory, which tracks the development of the COVID-19 virus.
As we learn to live with the virus, “we are building our repertoire against a wide variety of widths”Int so we are making it harder to find ways to avoid the virus,” Ayscue said. While the virus can adapt, “it”‘It will probably be less and less effective to do so,’ so there will be milder cases among those infected.
Significantly, the virus can cause a limited number of genetic changes, Perlman said. “It’s like a key in a lock,” he said. “That’s all you can do to turn the key to stay in the lock. It’s not infinite.”
Korber predicted that the virus could gradually mutate into a virus causing the common cold. “Very few of us will actually get sick, and fewer people will die, because many of us now have some immunity and our bodies are armed to fight back.”
“But it is very difficult to define what ‘slow’ means, and to predict its evolutionary trajectory, even over the next year or so,” she said. “It can be a bumpy ride.”