The Lambda coronavirus variant has been targeted for more study by the WHO.
It carries an unusual set of mutations and became dominant in Peru, where it was first identified.
But there is not enough information to know whether it is more transmissible yet, say experts.
As many nations wrestle with the Delta coronavirus variant, another is on the rise: the Lambda variant.
The variant is causing concern among officials in Latin America because of its unusual set of mutations.
Although the CDC is not yet tracking this variant, the World Health Organization (WHO) listed it as a variant of interest on June 15, and the UK added it to its list of variants under investigation on June 23.
"At the moment there's no evidence to suggest it's more aggressive than other variants," said Jairo Méndez Rico, an advisor on emerging viral diseases at the Pan-American Health Organization, the Financial Times reported.
"It's possible that it has a higher rate of contagion but more work needs to be done on it," he said.
The Lambda variant is in 29 countries, including the US
According to the WHO, the Lambda variant was first identified in Peru in August 2020.
But it has now spread to at least 29 countries.
It is most prevalent in Peru, where it made up 81% of all cases in May and June, according to the WHO.
There have been at least 563 infections in the US, according to the GISAID global variant reporting system.
Researchers at the University of Nevada, Las Vegas, for instance, detected Lambda in southern Nevada sewage water, suggesting that it is spreading in the community.
'Unusual' mutations could increase transmissibility
Lambda carries an unusual combination of mutations with the potential to change its ability to transmit or resist vaccination, the WHO has said.
"It has rather an unusual set of mutations, compared with other variants," said Jeff Barrett, director of the Covid-19 Genomics Initiative at the Wellcome Sanger Institute in the UK, the Financial Times reported.
In a study from the University of Chile published on July 1, which has not yet been reviewed by peers, scientists found that the variant was more contagious than the Alpha variant, first seen in the UK.
However, because this study was done in a lab, rather than in the real world, it is difficult to know how relevant to real life these results would be.
Barret told the Financial Times that it is difficult to assess how much more contagious the Lambda variant would be in a real-world setting because genetic sequencing facilities in South America are sparse.
Vaccines seem to remain effective against the Lambda variant
According to the WHO, mutations carried by the variant could theoretically increase its resistance to the protection conferred by vaccines.
In a tweet on Monday, Angela Rasmussen, a virologist at Georgetown University, said that evidence continues to suggest that vaccines work "very well" against all variants.
-Dr. Angela Rasmussen (@angie_rasmussen) July 6, 2021
A study from NYU Grossman School of Medicine offered more proof that the vaccines still work against Lambda, with some caveats.
The vaccines successfully stopped the virus from reproducing when samples from vaccinated people were tested on viruses modified to mimic the Lambda variant.
Too soon to worry?
Dr Faheem Younus, chief of infectious diseases at the School of Medicine at the University of Maryland, argued in a tweet concern about Lambda is "premature."
"It's a variant of interest, not a 'variant of concern'," he says.
-Faheem Younus, MD (@FaheemYounus) July 8, 2021
Variant of concern is a more serious designation the WHO can give when it has more evidence. Delta and Alpha were both named variants of concern as it became clear they were more contagious than other versions of the virus.
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