Coronavirus: Lambda variant of covid-19: what do we know about its origin in South America and its transmission capacity | Society

Lambda is already a “variant of interest” for the World Health Organization. This classification is tantamount to placing the line probably originating in Peru under careful but vigilant surveillance: it indicates that, based on the available evidence, C.37 has shown the potential to be more dangerous in humans in at least one of the dimensions. of concern about the virus (mainly its ability to infect or evade acquired immunity). Whether it will finally be, and to what extent, remains to be confirmed. But the testimonies collected in the Andean zone (Peru, but also Chile and Argentina) are not encouraging.

They are, yes, insufficient to draw solid conclusions. Perhaps the origin and geographical location of the lambda are linked to it. The history of lambda is inseparable from its emergence in an environment with a relatively weak genomic monitoring capacity. Without investment, installed capacity and transparency in the accumulated evidence, it is much slower and more difficult to measure the danger.

Andean origin

Pablo Tsukayama, coordinator of the Microbial Genetics laboratory at Cayetano Heredia University in Lima, is part of a team of researchers whose work was crucial in detecting, measuring and sizing the lambda initially, while it was still known by its lineage code: C. 37. According to the latest version of the study that characterizes it (still awaiting examination), lambda represented 100% of virus samples collected in Peru already in April 2020. It is this strong presence in specimens that leads them to hypothesize the Peruvian origin. .

Chile and Argentina are the other two target countries. “Argentina have reported less than 100 streaks but maybe they have a lot more,” Tsukayama said. He says it has to do with how each sample analyzes the Argentinian system. Each country has its own methodology, often limited by the need for savings or efficiency, or by established practices. In the Peruvian case, for example, Tsukayama himself claimed that it was not until April that they received the funds to produce an analysis like the one they ended up publishing, and that ‘he brought to light lambda.

The lack of open data doesn’t help either: on June 25, the Peruvian Ministry of Health highlighted its own figure for the percentage of lambda samples collected out of the total, standing at 71.1% between January and June. Several voices of science, including those of Tsukayama, then complained about the lack of access to the data behind: “We asked them to publish the data and they did not do it,” he reiterated.

But even so, the work of compiling initiatives such as GISAID or the collaboration between laboratories reflected in epidémie.info facilitates the relative scope of the variants. In this case, the hypothesis of Peruvian origin is reinforced by the notorious presence in neighboring Chile and Argentina, two countries with recent peaks of contagion that they have not been able to fully manage.

Localization has more to do with the context than with the intrinsic characteristics of the lambda, says Tsukayama, and reports the importance of mobility in explaining contagion. “What we have seen (with the variants) is that they appear and spread throughout the region.” But that’s because there are more movements, “introductions” in epidemiological terminology. “The success of a variant in a country depends not only on its degree of transmission, but also on the number of introductions.” lambda may have crossed borders with agility both for its competitive advantage and for the number of people who have moved it from one neighboring country to another.

More contagious?

When it comes to accurately assessing the higher transmissibility of lambda, Tsukayama considers that “the only evidence, preliminary but I think it is solid, is its rapid growth”, especially inside Peru. “Something that barely existed at the end of 2020, and which in March is already at 80%, means it probably has some sort of advantage. It is sown (with the presentations) and it broadens quickly ”. This is probably what caught the attention of WHO, which prompted the inclusion of the variant in the interest group.

However, what is the origin of this advantage, as well as its degree and durability, remains an open question. The WHO itself accepts that the evidence is not sufficient to conclude on concern, only to highlight the aforementioned potential for risk.

One of the reasons for the doubt is the weight of the environment. When rapid expansions of new variants are observed in specific contexts, speed perhaps has as much or more to do with some of its characteristics. For example: perhaps lambda has been able to develop with such agility thanks to the conditions of density and habitability of the cities where it has developed. There is no direct evidence to support such a hypothesis, but with the first waves of contagion it has been verified in Lima, Buenos Aires, São Paulo or Bogotá that SARS-CoV-2 to some extent follows the paths of overcrowding and worse living conditions. Urban. Additionally, along with other variations, such as the infamous and disturbing Delta, estimates of the increased percentage of contagion have adjusted downward, while still staying on top of its predecessors, as more data became available to remove contextual noise from the signal emitted by numbers such as the difference between secondary rates of contagion: how likely is a person carrier of SARS-CoV -2 lambda or delta version is transferred to another, compared to the one wearing previous variants.

To distinguish the contextual elements from those attributable to the genetics of the virus, researchers, like Tsukayama, continue to work: “We haven’t done these calculations yet, in part because we haven’t collected enough sequences yet. We are in this process. “

“The world has gotten used to quick proofs” on the variants, he adds, noting that this is a good thing, but also determined by the fact that a lot of them have been presented in situations of strong public attention and availability of resources to respond with agility to questions that arose, particularly in the United Kingdom, a country with health systems paired with researchers and institutions without equal epidemiologically and virologically. Something that so far has not necessarily accompanied the lambda, a variant typical of middle- and upper-income countries.

More surveillance and better vaccination

The other question on everyone’s minds about lambda, like any born or unborn variant, is how effective it is at avoiding the protection our immune system is endowed with through vaccination. On this point, the evidence is even rarer than on transmissibility. There are only a few studies available, both under laboratory conditions.

One, led by Chilean virologist Ricardo Soto Rifo, focused on the CoronaVac vaccine, from the Chinese laboratory Sinovac. By observing a group of volunteer health workers, they found that lambda exhibited “increased infectivity and immune escape capacity compared to the neutralizing antibodies” promoted by this vaccine. It remains to be seen the scope outside the laboratory of such a loss of relative protection, never complete.

In the other available study, like the previous one awaiting scientific peer review, a team from New York University found similar reductions for the Pfizer and Moderna vaccines, which the authors deemed “relatively minor. “.

Beyond nuance, and pending strong real-world evidence like the one we already have for the delta variant, what’s guessed is a trend with each new variant of minor but gradual deterioration in the protective ability of vaccines. . “It is virtually impossible to predict how a virus will mutate,” Tsukayama explains. But there are lessons. So far, we haven’t seen a much more pathogenic variant. But the good thing for the virus is to become more transmissible. This is why we are seeing gradual progress “in both transmissibility and immune escape, the second factor fueling the first.”

Robust and advanced systems of genomic surveillance and ex post evaluation are essential to monitor these progressive advances. Soto Rifo and his co-authors conclude in their study on antibodies and lambda that “mass vaccination campaigns in countries with high circulation of SARS-CoV-2 must be accompanied by strict surveillance which allows the identification of “mutations significant for immune evasion. Now that the WHO has officially identified lambda as a variant of interest, Tsukayama hopes more labs will join them to complete the studies needed to assess the extent of the threat it poses to the South American region. and for the rest of the world’s population. .

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