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 Scientists remain focused on Delta, now the dominant variant around
the world, but are tracking others to see what may one day take its
place.
DELTA - STILL DOMINANT
The Delta variant first detected in India remains the most
worrisome. It is striking unvaccinated populations in many countries
and has proven capable of infecting a higher proportion of
vaccinated people than its predecessors.
The WHO classifies Delta as a variant of concern, meaning it has
been shown capable of increasing transmissibility, causing more
severe disease or reducing the benefit of vaccines and treatments.
According to Shane Crotty, a virologist at the La Jolla Institute
for Immunology in San Diego, Delta's "superpower" is its
transmissibility. Chinese researchers found that people infected
with Delta carry 1,260 times more virus in their noses compared with
the original version of the coronavirus. Some U.S. research suggests
that the viral load in vaccinated individuals who become infected
with Delta is on par with those who are unvaccinated, but more
research is needed.
While the original coronavirus took up to seven days to cause
symptoms, Delta can cause symptoms two to three days faster, giving
the immune system less time to respond and mount a defense.
LAMBDA – ON THE WANE
The Lambda variant had attracted attention as a potential new
threat, but this version of the coronavirus, first identified in
Peru in December, appears to be receding.
Although cases involving Lambda were rising in July, reports of this
variant have been falling globally for the past four weeks,
according to data by GISAID, a database that tracks SARS-CoV-2
variants.
The WHO classifies Lambda as a variant of interest, meaning it
carries mutations suspected of causing a change in transmissibility
or causing more severe disease, but it is still under investigation.
Lab studies show it has mutations that resist vaccine-induced
antibodies.
MU - ONE TO WATCH
Mu, the variant formerly known as B.1.621, was first identified in
Colombia in January. On Aug. 30, the WHO designated it as a variant
of interest due to several concerning mutations, and assigned a
Greek letter name to it.
Mu carries key mutations, including E484K, N501Y and D614G, that
have been linked with increased transmissibility and reduced immune
protection.
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 According to the WHO's Bulletin
published last week, Mu has caused some larger
outbreaks in South America and Europe. While the
number of genetic sequences identified as Mu
have fallen below 0.1% globally, Mu represents
39% of variants sequenced in Colombia and 13% in
Ecuador, places where its prevalence has
"consistently increased," WHO reported.
The global health agency said it continues to monitor Mu for changes
in South America, especially in areas where it is co-circulating
with the Delta variant. Maria van Kerkhove, head of WHO's emerging
diseases unit, said circulation of the variant is decreasing
globally but needs to be observed closely. In a press briefing last
week, White House chief medical advisor Dr. Anthony Fauci said U.S.
officials are watching it, but so far Mu is not considered an
immediate threat.
MORE ON THE WAY?
Getting more people vaccinated against COVID-19 is critical as large
groups of unvaccinated people give the virus more opportunity to
spread and mutate into new variants.
That effort must be stepped up internationally to keep variants from
emerging unchecked among the populations of poor nations where very
few people have been inoculated, experts say.
Even so, while the current vaccines prevent severe disease and
death, they do not block infection. The virus is still capable of
replicating in the nose, even among vaccinated people, who can then
transmit the disease through tiny, aerosolized droplets.
To defeat SARS-CoV-2 will likely require a new generation of
vaccines that also block transmission, according to Dr. Gregory
Poland, a vaccine developer at the Mayo Clinic. Until then, Poland
and other experts say, the world remains vulnerable to the rise of
new coronavirus variants.
(Reporting by Julie Steenhuysen; Additional reporting by Ahmed
Aboulenein in Washington; Editing by Michele Gershberg and Bill
Berkrot)
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