Debunking the idea viruses evolve to become less virulent

As proof mounts that the omicron variant is less lethal than prior COVID-19 strains, one oft-cited rationalization is that viruses at all times evolve to become less virulent over time.

The downside, consultants say, is that this idea has been soundly debunked.

The idea that infections have a tendency to become less deadly over time was first proposed by notable bacteriologist Dr. Theobald Smith in the late 1800s. His idea about pathogen evolution was later dubbed the “legislation of declining virulence.”

Simple and stylish, Smith’s idea was that to guarantee their very own survival, pathogens evolve to cease killing their human hosts. Instead, they create solely a light an infection, permitting individuals to stroll round, spreading the virus additional afield. Good for the virus, and, arguably, good for us.

But over the previous 100 years, virologists have discovered that virus evolution is extra chaotic. Virus evolution is a recreation of probability, and less about grand design.

In some circumstances, viruses evolve to become extra virulent.

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Continued virus survival, unfold and virulence are all about the evolutionary pressures of a number of components, together with the variety of individuals out there to infect, how lengthy people stay after an infection, the immune system response and time between an infection and symptom onset.

Unfortunately, which means it is almost inconceivable to predict the way forward for the pandemic, as a result of viruses do not at all times evolve in a predictable sample.

There have been 1000’s of recognized COVID variants, every with unique mutations. But most new variants emerge after which rapidly die out, unable to compete with the reigning dominant variant.

Some variants, nevertheless, have clear “benefits to continued survival, reminiscent of people who evade the immune system and unfold simply,” stated Dr. Abir Hussein, affiliate medical director for an infection presentation and management at University of Washington Medical Center.

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Experts warn that it is necessary to assess the severity of omicron in the context of present immunity by means of vaccines and prior infections.

“It is tough to decide with new variants like delta and omicron if variants are evolving to be extra or less virulent. This is as a result of these variants emerged at a time after we had a great deal of immunity to SARS-CoV-2 in sure international locations,” stated Andrew Pekosz, a professor of microbiology at Johns Hopkins University Bloomberg School of Public Health.

People who’re vaccinated or just lately contaminated could have milder signs in the event that they expertise a breakthrough an infection or a reinfection, research present.

“This will not be as a result of the variant is less virulent, however as a result of your immune system was primed from prior vaccination and an infection,” stated Pekosz.

Experts say omicron shouldn’t be taken frivolously or regarded as a less deadly type of COVID. Even if less lethal, the omicron variant can also be considerably extra transmissible, main to extra deaths total.

The U.S. Centers for Disease Control and Prevention predict that 22,000 extra individuals might die of COVID-19 over the subsequent two weeks.

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People who’re unvaccinated stay considerably extra at-risk, with officers estimating they’re 17 occasions extra probably to be hospitalized and 20 occasions extra probably to die of COVID-19 in contrast to people who find themselves vaccinated.

“The out there COVID vaccines present immunity for a variety of variants and proceed to be the first line of protection,” stated Dr. John Brownstein, chief innovation officer at Boston Children’s Hospital and an ABC News contributor.

As for the way forward for the pandemic, consultants say new variants might emerge in the future, however they will not be straightforward to predict.

Jess Dawson, M.D., a masters of public well being candidate at Johns Hopkins Bloomberg School of Public Health, is a contributor to the ABC News Medical Unit.

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