September 23, 2021

Biology Reporter

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How will Delta develop?  So science tells us

How will Delta develop? So science tells us

A daily summary of all the major events surrounding the Covid-19 Delta outbreak as New Zealand plunges into confinement for the fifth time. Video / NZ Herald

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The COVID-19 pandemic is actually a dramatic display of evolution. The theory of evolution explains much of what has already happened, predicts what will happen in the future, and suggests the most likely effective management strategies.

For example, evolution explains why the delta variant spreads faster than the original Wuhan strain. It explains what we can see with future variables. It suggests how we can respond to public health efforts.

But Delta is not the end of the story for SARS-CoV-2, the virus that causes Covid-19. What the theory of evolution tells us will come later.

Remind me again how viruses evolve?

evolved It is the result of random mutations (or errors) in the viral genome during reproduction. Few of these random mutations It will be useful for the virusWhich has some advantages. It is likely that copies of these beneficial genes will survive into the next generation thanks to the process of natural selection.

New viral strains may also evolve reassembleWhen viruses acquire genes from other viruses or even from their hosts.

In general, we can expect evolution to favor the virus strains that lead to a steeper epidemiological curve, leading to more cases faster, leading to two predictions.

First, the virus must become more portable. An infected person is likely to infect more people; Future versions of the virus will have a higher reproduction number, the R number.

Second, we can also expect evolution to shorten the time it takes humans to infect others (a shorter “sequence period”).

Both expected changes are clearly good news for the virus, but not for its host.

Oh, that’s what Delta says

Explain this theory Why Delta is embracing the world now The original Wuhan strain was named.

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The original Wuhan strain had an R value of 2-3, but a Delta R value of about 5-6 (some researchers say this number is So it is higher). So a person with delta infection is at least twice as likely to get infected as many people as the original Wuhan variety.

There is also some evidence that Delta has The period of the series is much shorter Compared to the original Wuhan strain.

may be related to Higher viral load (more viruses) in a person with delta than previous strains. This allows delta to pass faster after an injury.

Higher virus titer may also facilitate delta transmission Abroad I’m Bo”jump connection“.

Do vaccines affect the growth of the virus?

We know that Covid-19 vaccines designed to protect against the original Wuhan strain work against Delta, but it is less effective. This is what the theory of evolution predicts. Avoidable viral variants have an evolutionary advantage.

So we can expect arms race Between vaccine makers and the virus, vaccines are trying to keep pace with the evolution of the virus. Therefore, we will likely see that we run regularly reminder shotsDesigned to circumvent these new variants, such as influenza vaccines.

Covid-19 Vaccine reduce your chance They can transmit the virus to other people, but they do not completely prevent it from being transmitted. The theory of evolution gives us a cautionary tale.

tam flexibility between the passability and the degree of infection (virulence) with most pathogenic microorganisms. This is because you need a certain amount of virus to be transmitted.

If vaccines are not 100 percent effective in preventing transmission, we can expect a shift in the trade-off toward higher virulence. In other words, the theory predicts that over time, as a side effect of transmitting the virus from vaccinated people, it will become more harmful to unvaccinated people.

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What about future variables?

In the short term, it is very likely that evolution will continue to “tune” the virus:

• R value will continue to increase (more people will be infected in one generation);
• the sequential interval will decrease (people will become infectious faster);
Variants will make vaccines less effective (avoid vaccination).

But we don’t know how far these changes could go or how fast.

Some scientists think the virus may be on the way.”peak efficiencyBut maybe still Some tricks in my sleeve.

Scientific Advisory Group on Emergencies to the Government of Great Britain (SAGE) Investigation scenarios for the long-term evolution of the virus.

He says there will almost certainly be an “antigenic drift”; Accumulation of small mutations makes existing vaccines less effective, so it will be necessary to boost modified vaccines.

He then says that the more dramatic changes in the virus (“antigenic shift”) that could occur as a result of recombination with other human coronaviruses is a “realistic possibility”. This will require a major redesign of vaccines.

SAGE also believes there is a realistic possibility of “reverse zoonosis” where the virus may be the most pathogenic (harmful) to humans or may bypass existing vaccines. This would be a scenario in which SARS-CoV-2 infects animals before being transmitted to humans. We have already seen SARS-CoV-2 infection Mink, cats and rodents.

Will the virus become more deadly?

Versions of the virus that make its host very sick (highly pathogenic) are usually chosen against it. This is because people will be more likely to die or be isolated, reducing the risk of transmitting the virus to other people.

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SAGE believes this process is unlikely to make the virus less virulent in the short term, but it is a realistic long-term possibility. However, SAGE says there is a real possibility that more virulent strains may evolve through recombination (which is known to cause other coronaviruses).

So the answer to this important question is that we don’t really know if the virus will become more deadly over time. But we cannot expect the virus to magically become harmless.

Are humans evolving to catch up?

Unfortunately, the answer is no. Humans don’t reproduce fast enough, accumulating beneficial mutations fast enough for us to stay ahead of the virus.

Nor does the virus kill most infected people. And in countries with well-equipped health systems, not many people of childbearing age are killed. So there is no “selection pressure” on humans to mutate positively to stay ahead of the virus.

What about epidemics in the future?

Finally, the evolutionary theory contains a warning of future pandemics.

A genetic mutation allows a virus of a mysterious and relatively rare species (such as bats) to reach the most common and widespread species of large animals on the planet – humans – will be highly chosen for.

So we can expect epidemics in the future When animal viruses are transmitted to humans as they were in the past.

Hamish McCallum is director of the Center for Planetary Health and Food Safety at Griffith University in Queensland, Australia.

This article has been republished with conversation Under Creative Commons License. is reading original article.

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