The Washington Post - USA (2022-05-02)

A8 EZ RE THE WASHINGTON POST.MONDAY, MAY 2 , 2022

it, to observe the locations of mu-

tations and draw inferences for

why they matter. On Friday, asked

about BA.2.12.1, and why it is

spreading, he noted that it has a

mutation, named S704L, that

probably destabilizes a portion of

the spike protein on the virus’s

surface. That essentially loosens

up part of the spike in a way that

facilitates infection.

This S704L mutation distin-

guishes this subvariant from BA.2.

The “704” refers to the 704th

position for an amino acid on a

chain of roughly 1,100 amino acids

that form the protein. The S is one

type of amino acid (“serine”) seen

in the original strain of the virus,

Osterholm, a University of Minne-

sota infectious-disease expert. “Ev-

ery day I wake up, I fear there will

be a new subvariant that we will

have to consider.... We’re seeing

subvariants of subvariants.”

Garry, the Tulane scientist,

points out that mutations in the

virus do not change its appearance

dramatically. In fact, he said, even

the heavily mutated variants don’t

look much different from the orig-

inal Wuhan strain, or different

from other coronaviruses that

cause common colds. These are

subtle changes.

Garry has a software program

that allows him to create a graphic

image of the virus, and even rotate

have mutations that were seen in

earlier variants and could lead to

immune evasion. Caseloads there

are rising. New laboratory re-

search by the Africa Health Re-

search Institute, posted online

Sunday but not yet peer-reviewed,

indicated that the emerging sub-

variants are adept at eluding the

neutralizing antibodies seen in

people who recovered from infec-

tions with the original omicron

variant. The authors of the study

concluded that BA.4 and BA.

have the “potential to result in a

new infection wave.”

“The evolution is much more

rapid and expansive than we ini-

tially estimated,” said Michael T.

in greater numbers once an infec-

tion has begun — increasing the

viral load in the person and, com-

mensurately, the amount of virus

that is shed, potentially infecting

other people.

The other strategy involves the

workaround of immunity. The hu-

man immune system, when

primed by vaccines or previous

infection to be alert for a specific

virus, will deploy antibodies that

recognize and neutralize it. But

mutations make the virus less fa-

miliar to the immune system’s

front-line defense.

The subvariants keep coming:

Scientists in South Africa have

identified BA.4 and BA.5, which

more transmissible than alpha,

and alpha was more transmissible

than earlier variants that did not

have the glory of a Greek alphabet

name.

Most mutations are not advan-

tageous to the virus. But when a

mutation offers some advantage,

the process of natural selection

will favor it.

There are two fundamental

ways that the virus can improve its

fitness through mutation. The

first could be described as me-

chanical: It can become innately

better at infecting a host. Perhaps

it improves its ability to bind to a

receptor cell. Or perhaps the mu-

tation allows the virus to replicate

to the Centers for Disease Control
and Prevention. The CDC said the
subvariant has rapidly spread in
the Northeast in particular, where
it accounts for the majority of new
infections.
“We have a very, very conta-
gious variant out there. It is going
to be hard to ensure that no one
gets covid in America. That’s not
even a policy goal,” President
Biden’s new covid-19 coordinator,
Ashish Jha, said in his inaugural
news briefing Tuesday.
He was answering a question
about Vice President Harris, who
recently tested positive for the vi-
rus and went into isolation. Harris
had recently been boosted for the
second time — her fourth shot of
vaccine.
Her case highlights what has
become painfully obvious in re-
cent months: No amount of vacci-
nation or boosting can create a
perfect shield against infection
from SARS-CoV-2. What the vac-
cines do very well, however, is
greatly reduce the risk of severe
illness. That is hugely consequen-
tial as a matter of public health, as
is the wider use of therapeutics,
such as the antiviral Paxlovid.
The vaccines currently de-
ployed were all based on the ge-
nomic sequence of the original
strain of the virus that spread in
late 2019 in Wuhan, China. They
essentially mimic the spike pro-
tein of that version of the virus and
trigger an immune response that
is protective when the real virus
shows up.
But the variants that have
emerged can evade many of the
neutralizing antibodies that are
the immune system’s front line of
defense.
“It’s evolving at a fairly rapid
rate,” said Jesse Bloom, a compu-
tational biologist at the Fred
Hutchinson Cancer Research Cen-
ter in Seattle. “I do think we need
to aggressively consider whether
we should update vaccines, and do
it soon.”
BA.2.12.1 brings the novel coro-
navirus up another step on the
contagiousness scale. Its close rel-
ative, BA.2, was already more
transmissible than the first omi-
cron strain that hit the country in
late 2021.
And omicron was more trans-
missible than delta, and delta was

MUTATIONS FROM A

Coronavirus zigs and zags, complicating control efforts

MATT MCCLAIN/THE WASHINGTON POST

Metro users saw the end of a mask-wearing requirement last month, but scientific research indicates that the coronavirus and its many mutations will be sticking around.

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