Dear Editor,
New variants of SARS-CoV-2 have been emerging since the beginning of the COVID-19
pandemic [1]. The virus evolves into new variants to attain better fitness than the
original viral strain; thus, the variants are thought to infect the human host more
efficiently and successfully. This evolutionary tendency is not unique to SARS-CoV-2;
all viruses are known to mutate to gain survival advantages, including high receptor-binding
affinity, infectivity, replication fitness, high transmissibility and virulence, resistance
to neutralizing antibodies and immune evasion, and augmenting the disease severity
and reinfection chance [2]. When writing this correspondence, The World Health Organization
had listed two currently circulating variants of concern (VOCs; Delta and Omicron),
three previously circulating VOCs (Alpha, Beta, and Gamma), eight previously circulating
variants of interest (VOIs; Epsilon, Zeta, Eta, Theta, Iota, Kappa, Lambda, and Mu),
and two variants under monitoring (VUMs; B.1.640 and XD).
The number of new cases of SARS-CoV-2 has been decreasing globally as of April 2022;
however, >200 countries have been experiencing the latest case surges due to the Omicron
VOC [3]. On March 25, 2022, the U.K. Health Security Agency announced that a new recombinant
BA.1–BA.2 variant of Omicron (designated XE) was detected through gene sequencing
first on January 19, 2022. Subsequently, more cases were detected in East of England,
London, and the South East. The same agency announced that 637 cases were positive
with XE, and that all possible recombinant viral variants were closely monitored,
but the transmissibility of the variant was unknown (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1063424/Tech-Briefing-39-25March2022_FINAL.pdf).
Mixed infections by different sublineages of a VOC or even different VOCs can occur
if they are actively circulating together. Such coinfections may cause emergence of
new recombinant subvariants likely with a better evolutionary survival fit. XE thus
could cause infections with higher circulation advantage among the human hosts as
these have been observed during the COVID-19 pandemic. The World Health Organization
follows the news about this variant; other countries including Thailand have reported
the detection of XE [4]. Meanwhile, a different recombinant variant termed Deltacron
was first reported in Paris in February 2022. This variant has resulted from the recombination
of the Delta and Omicron VOCs. Since February 2022, different variants of this hybrid
have been reported in other parts of Europe and the U.S.A [5].
Future perspective
Detection of XE and different forms of the “Deltacron” variants in distant countries
suggests that the same or different variants will soon be appearing and reported by
other countries, too; thus, a rise in numbers of COVID-19 cases is expected. However,
experiencing another pandemic peak boosted by such variants, as was experienced with
the Delta, Beta, Omicron, and Gamma [6,7] variants, is difficult to predict.
The present global overview of the progress of the pandemic and global countermeasures
indicates that >11 billion doses of an approved anti-COVID-19 vaccine were administered,
and only <65% of the world population have received at least one dose of a vaccine
(https://ourworldindata.org/covid-vaccinations?country=OWID_WRL). This big vaccination
shortfall gravely challenges the future global management of the pandemic. Indeed,
the low global vaccination rate encourages emergence of the SARS-CoV-2 subvariants
because the virus can still circulate actively among some members of the communities,
including unvaccinated adults or children, immunocompromised individuals, or those
older than ≈75 years. Meanwhile, many countries have eased or lifted the COVID-19
countermeasures regarding mass-gatherings and have opened their borders to international
travel. Although XE characteristically may be like Omicron, and a profound change
in disease severity or transmissibility compared with those by the precursor strains
is unexpected, emergence of another VOC could majorly threaten the public health globally,
especially if a more virulent strain surges in countries with low vaccination rates.
We believe equitable global vaccination campaigns must be reinforced to better prepare
the world for emergence of an unexpectedly virulent variant.
Please state any conflicts of interest
None.
Please state any sources of funding for your research
This study received no specific grant from any funding agency in the public, commercial,
or not-for-profit sector.
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Author statement
Farid Rahimi: Conceptualization, Data Curation, Writing – Original Draft, Writing
– review & editing.
Amin Talebi Bezmin Abadi: Conceptualization, Data Curation, Writing – Original Draft,
Writing – review & editing.
All authors critically reviewed and approved the final version of the manuscript before
submitting.
Guarantor
Both authors.
Data statement
Data not available/not applicable.
Funding
None.
Provenance and peer review
Not commissioned, internally peer-reviewed.
Declaration of competing interest
Authors have no competing interests to declare.