Travel restrictions ?: Why are the coronavirus variants affected?

B.1.1.7 … B.1.351 … B.1.1.28 … They look like the codenames of a spy movie, but they are the variants of the coronavirus this cause concern of epidemiologists and health authorities around the world. So much so that the Minister of Health of the Province of Buenos Aires, Daniel Gollán, today anticipated that travel to neighboring countries could even be limited to prevent their entry into Argentina.

As explained by virologist Humberto Debat, researcher at INTA and member of the Argentine interinstitutional genomics project of SARS-CoV-2 (COUNTRY), I already know reported constellations of mutations indirectly associated with biological changes in the virus, but in rare cases, this initial identification is supplemented by epidemiological or clinical information suggesting that it deserves special attention.

“At that time, according to the World Health Organization, only exists in the whole world three variants classified as ‘worrying’: one originally established in the B.1.1.7 lineage (in the UK), another in the B.1.531 lineage (in South Africa) and one in the B.1.1.7 lineage B.1.1.28 (in Manaus, Brazil))», Explains Debat.

The expert points out that the first has already been reported in more than 94 countries, it is between 50% to 70% more transmissible and 60% to 65% more serious. The replication of the epidemiological curves after arriving in different countries, such as Israel, Portugal, Denmark and the United States, also confirms that it is more contagious and causes more severe symptoms.

The second, detected at this stage in 48 countries, was originally associated with a significant increase in its frequency in South Africa, where it was established. One thinks that it is more transmissible, although it is not yet clear. However, certainty is mounting about its greater ability to “evade” immune, which decreases neutralization with monoclonal antibody therapies, convalescent sera and even the effectiveness of some vaccines, which has led the government from that country to return nearly two million doses of Oxford / AstraZeneca Immunization.

The third, dubbed P.1, was initially reported on January 12 in Manaus, Amazonas state. “In recent days, a series of disturbing reports suggest that this variant is between 1.2 and 2.4 times more transmissible, which is associated with a significant increase in viral load and 25% to 60% probability of reinfection, as well as immune leaks seen in experiments in vitro. In addition, it showed a decrease in neutralization by the sera of those immunized with the CoronaVac vaccine ”, underlines Debat. However, he adds that an article published yesterday and an unofficial statement raised good expectations. The first argues that the sera of those immunized with the vaccine developed by Pfizer / BioNTech are able to neutralize both this variant and that of South Africa and the United Kingdom, and that the immunization developed by Oxford / AstraZeneca is effective against the Manaus variant.

PAIS genomic monitoring reports indicated that So far, four samples of the UK variant have been identified in Argentina (two of them with no travel history or epidemiological link to travelers, suggesting that it would already have community circulation in the country. ); the presence of that of South Africa was not detected, and that of Manaus was only identified in one traveler and in close contact with another traveler. The Malbrán Institute recorded two other cases, also imported, so there is still no conclusive data on the circulation of the latter in the country.

Apart from that, “during genomic monitoring, we have already detected more than 45 samples compatible with the so-called Rio de Janeiro variant, which is associated with immune leakage,” explains Debat. At this time, the substitution which characterizes it is present in 20% of the AMBA tests, which is a wake-up call ”. Fortunately, it is not classified as “disturbing”.

In addition, two other variants triggered alarms. These are the ones originally found in California and New York. Among the former, there is very little evidence to suggest that its prevalence has increased very rapidly or that it is more transmissible. The second, detected on November 15, now represents 12% of viruses sequenced in New York. “Its central markers are associated with immune leakage,” explains Debat. This, added to its apparent increase in frequency, makes it one of the “interesting” ones.

One of the issues currently being analyzed by virologists is the rate at which these viral changes can appear. In the case of SARS-CoV-2, accumulated around 24 to 26 mutations per year, which is verified when comparing samples sequenced in January 2020 with isolates from July. But that could change.

“Until November, the virus behaved in an extremely stable and systematic manner,” explains the scientist. We sequenced a viral genome and by the number of mutations we were able to estimate without too many errors in which month the sample had been taken. Suddenly, in November, these variants appear almost simultaneously in different regions of the planet, in an independent and converging process, as they share certain markers, but the most interesting was how different they were from the most similar virus sequenced until this moment. In other words, they had acquired a large number of mutations in a short period of time. It has been described as an acceleration of the evolutionary process of the virus. And the most plausible explanation is that diversity is fertile ground for the immunocompromised. From there, the pandemic begins to change. “

According to the researcher, the process of establishing new lineages in a place is like a kind of sparks that can generate a fire. The more sparks there are, the more likely a variant is to fall into place. “In virology, there is what is called the” inoculum pressure “, which can be extrapolated to the epidemiological level: the more virus there is, the more there is the probability of contagion and that these new lines are established. . If you could get people to self-isolate for 14 days upon arrival from overseas, no travel should be restricted. But as this is often not possible, it may be necessary to think of other measures, ”he concludes.

More information