16 | New Scientist | 1 January 2022

Preview of 2022

7

W

E HAVE been watching

evolution in action as one

coronavirus variant after another

emerges and triggers further waves

of infections around the world.

There is every reason to think this

will continue during 2022 – and there

is no guarantee that future variants

will be any less dangerous.

For the SARS-CoV-2 coronavirus,

survival is all about infecting as many

people as possible. Variants that are

better at spreading will outcompete

other variants. A key part of this is

transmissibility. When the original

virus began spreading, every

infected person infected two or

three others on average. Delta infects

six or seven. Omicron seems to be

even more contagious.

It isn’t yet fully understood

how the virus is becoming more

infectious. But with delta, it might

be because it is better at replicating

itself, meaning infected people

shed more of the virus.

Infecting people is no longer as

easy as it used to be, however. Most

people in the world now have some

degree of immunity because of past

infection or vaccination. So variants

such as omicron are evolving to evade

this immunity, typically through

changes in the outer spike protein,

the main target of our antibodies.

There is a limit to how much more

infectious the virus can become, but

there may be no limit to its ability

to evade our immune response.

As happens with human flu viruses,

we may see the continual emergence

of new variants that evade immunity

enough to cause wave after wave

of infections.

It is possible that, over time,

different viral lineages will persist

and diverge, rather than successive

variants wiping out all others and

sweeping to dominance. This could

require different vaccines to be

combined into a single dose,

as is done with the flu vaccine.

It is often claimed that new

viruses will evolve to cause milder

symptoms. But because SARS-CoV-

is most infectious just before

symptoms appear, there is little

selective pressure for it to do this.

Smallpox was highly lethal and might

have become worse over time. Flu still

exacts a high annual death toll.

Another concern is that the virus

might be circulating in several other

animals, generating new variants

that could jump back into people.

While it is possible that future

variants may cause more severe

illness in people with no immunity,

most people in the world do now

have some immunity. This is likely to

continue to provide some protection

against severe illness even if it fails to

prevent infections.

But we can expect this immunity

to fade over time. Even if you have

already had a booster shot, you could

well find yourself standing in line to

get yet another jab or two in 2022 to

protect you from rho, sigma, upsilon

or maybe even omega. ❚

Covid-

More SARS-CoV-2 variants

are inevitable. Michael Le Page

reveals what to expect from them

The virus will evolve further

The delta variant,

viewed using an

electron microscope

“ Most people around the

world now have some

immunity from past

infection or vaccination”

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