While the world reels under the effects of the Delta variant, a new Covid-19 mutation is now on the radar of several countries.
The Lambda variant, or C.37, believed to have originated from Peru, was designated as a “variant of interest” by the World Health Organization (WHO) on June 14. A variant of interest categorisation is a level below the “variant of concern.”
There are currently four variants of interest, which are characterised by the presence of mutations that are associated with increased transmissibility, severity of disease, or the ability to evade immunity from vaccines or past infections. This does not mean that these variants have been yet confirmed to be more transmissible or to cause more severe infections—only that the genetic structure of the mutated virus points to the possibility of these happening. In addition to these criteria, variants of interest are also classified when there are known cases of community transmission or Covid-19 clusters.
Though the Delta variant, a variant of concern first detected in India and thus far believed to be the most transmissible and resilient variant of Covid-19, dominates most infections across the world, six cases of the Lambda variant have now been found in the UK, all linked to international travellers. There are no cases of the variant reported in India yet.
Initially known as the “Andean variant” after being detected in Peru in December 2020, the C.37 variant drew little notice beyond Latin America as the Alpha variant, first seen in Kent, England around the same time, preoccupied the world.
When the WHO moved to rechristen variants to discourage them from being associated with the place where they surfaced, the variant was renamed for the Greek letter lambda.
Is Lambda more transmissible than Delta?
“There is currently limited evidence available about this variant,” Dr Alicia Demirjian, Covid incident director at Public Health England (PHE), told BBC Science Focus magazine. The PHE is currently testing the viral strain in laboratories to identify its characteristics and its possible impact on community transmission. “There is currently no evidence that this variant causes more severe disease or renders the vaccines currently deployed any less effective,” it said.
As Peruvian microbiologist Pablo Tsukuma pointed out in a long Twitter thread on the Lambda in May, variations in regional capacity for sequencing explain why we know so much less about Lambda than Alpha, or even Delta, right now.
Where in the world is Lambda?
As of late June, Lambda has been found in more than two dozen countries, according to the UK government, which designated it a “variant under investigation” on June 23, citing its “international expansion.”
It’s so far widely prevalent only in Latin America, including Peru, Chile, Ecuador, and Argentina. In Peru, for example, it accounted for 81% of the cases sequenced between mid-April and mid-June—from less than 1% when first discovered. It’s also the country that has reported the highest official per capita death rate from Covid-19.
And so far, in places where the Delta variant is also present, the latter appears to spread far more easily. Portugal for example saw its first Lambda cases in April—but in Portugal, like in the UK, the Delta accounts for the vast share of new cases.