Sunday, January 16

Will Covid-19 become less dangerous as it evolves? | Coronavirus


The pandemic has been riddled with slogans, but in the last two weeks they have been repeated with increasing frequency: “Variants will evolve to be milder” and “Covid will become endemic.” However, experts caution that neither of these things can be taken for granted.

Those who claim that viruses become less deadly over time often cite influenza. The two flu viruses responsible for the 1918 Spanish flu and 2009 swine flu pandemic eventually evolved to become less dangerous. However, the 1918 virus is believed to have grown more lethal before becoming milder. And other viruses, like Ebola, have become more dangerous over time.

“It is a fallacy that viruses or pathogens become milder. If a virus can continue to spread and cause many diseases, it will, ”said Professor David Robertson, head of viral genomics and bioinformatics at the University of Glasgow Center for Virus Research.

Viruses aim to create as many copies of themselves and spread as widely as possible. Although it’s not always in their best interest to kill their hosts, as long as they are broadcast before this happens, it doesn’t matter. Sars-CoV-2 does not kill people during the period when it is most infectious; people tend to die two to three weeks after getting sick. As long as it doesn’t evolve to make people so sick that they don’t mix with other people while infectious, the virus doesn’t care if there are a few victims along the way.

It’s also not clear that Sars-CoV-2 is getting progressively milder. Omicron appears to be less severe than the Alpha or Delta variants, but both variants caused more severe disease than the original Wuhan strain. Importantly, viral evolution is not a one-way street: Omicron did not evolve from Delta and Delta did not evolve from Alpha; it’s more random and unpredictable than that.

“These [variants of concern] They don’t go from each other, so if that pattern continues and another variant appears in six months, it could be worse, ”said Robertson. “It is important not to assume that it is inevitable that Omicron is the end of the Sars-CoV-2 evolution.”

There is a chance that Omicron is so transmittable that it has hit a ceiling where future variants will have a hard time getting past it. But just a few months ago, people were saying the same thing about Delta. Additionally, Omicron is likely to continue to evolve. “What could happen is that since Omicron infects so many people, it is more difficult for the first Omicron [variant] to continue to be so successful, and that creates room for a virus that is better at evading the immune response, “said Robertson.

What about the idea that Sars-CoV-2 could become endemic? Politicians tend to use this as a proxy to get on with our lives and forget that Covid-19 exists. What actually means endemic is a disease that is constantly present, but where infection rates are predictable and do not get out of control.

“Smallpox was endemic, polio is endemic, Lassa fever is endemic and malaria is endemic,” said Stephen Griffin, associate professor of virology at the University of Leeds. “Measles and mumps are endemic, but they depend on vaccination. Endemic does not mean that something loses its teeth at all. “

As more and more people develop immunity to Sars-CoV-2 or recover from infection, the virus is less likely to trigger serious illness. But then it could evolve again. The good news is that this becomes less likely as more of the world’s population is vaccinated, because the fewer people who are infected, the less chance the virus has to evolve, but we’re not close to that yet. Even in the UK, there are large numbers of unvaccinated people and it is unclear how long the protection from boosters will last.

“The idea that we will achieve endemicity in the near term also seems a bit contrary to the fact that we just had several weeks of massive explosive exponential growth, and before that, we were still seeing exponential growth from Delta,” Griffin said. .

Transforming Covid into a disease we can really live with requires more than a national vaccination campaign and wishful thinking; it requires a global effort to improve surveillance for new variants and support countries to address outbreaks at source when they arise. It also requires more investment in air purification and ventilation to reduce transmission within our own borders, if we mix indoors.

Everyone hopes that the coronavirus will evolve to become milder and that the covid will become endemic, or rather, manageable enough not to ruin our daily lives. But these are hopes, not facts, and repeating these mantras will not make them happen any faster.


www.theguardian.com

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