Carlos Serrano (@carliserrano) – BBC News World
posted on 05/04/2021 08:38
Unlike other parts of the world, Brazil is experiencing its worst moment in the pandemic, with an increasing number of infections and deaths due to covid-19.
The increase in the number of cases in recent days has been attributed in part to the spread of a highly contagious variant of the SARS-CoV-2 virus, called P.1, which is believed to have originated in Manaus.
Experts warn that what is happening in Brazil is just one example of the importance of monitoring the emergence of variants of the virus in Latin America.
This monitoring is known as genomic surveillance and, according to experts consulted by BBC News Mundo, the BBC’s Spanish service, Latin America is lagging behind in this task.
Experts agree that, although progress has been made, genomic surveillance needs to be strengthened in the region. And they warn against the risk of not being done on a large scale.
“Latin America needs strong genomic surveillance. In most countries, it is still minimal,” epidemiologist Zulma Cucunubá, a specialist in infectious diseases and public health at Imperial College London, in the United Kingdom, wrote on Twitter in early March. United.
“We don’t know what’s going on with the SARS-CoV-2 variants in the region.”
The genetics of the virus
Each SARS-CoV-2 virus has a genetic code expressed in a sequence of 30 thousand letters.
This set of letters is known as the virus genome – and it is what gives him instructions on how to act and transmit himself.
In addition, these letters act as a “historical archive of the evolution of the virus”, as Fernando González Candelas, professor of genetics at the University of Valencia, in Spain, explains in an article published on the academic news site The Conversation.
Each time the virus infects another person, there is a possibility of mutating, something that is understood as a characteristic of viruses.
Thus, scientists can say that a virus has mutated when it realizes that some of the letters in its genome have changed.
Mutations happen all the time, but when a group of viruses share the same set of mutations, they form what is known as a variant.
During the pandemic, variants of SARS-CoV-2 were identified in different parts of the world.
Some of them are what are technically known as “worrying variants” because they have the potential to be more contagious, cause more serious illness or reduce the effect of vaccines.
So far, at least three worrying variants have been detected:
– B.1.1.7, first identified in the United Kingdom;
– B.1.351, first identified in South Africa;
– P.1, first identified in Brazil.
“The virus is not a static unit, it constantly changes,” Julián Villabona, a molecular epidemiologist at the Center for Mathematical Modeling of Infectious Diseases at the School of Hygiene and Tropical Medicine in London, told the BBC News Mundo.
“If he gets the chance, it will change to allow him to infect more people or, in some cases, cause more serious illnesses.”
These variants were identified thanks to the fact that scientists share thousands of virus genomes in a large global database.
This database is called GISAID, which stands for Global Initiative for Sharing All Influenza Data.
The name is due to the fact that it was originally created to monitor the genome of the flu virus.
What the GISAID researchers do is map the 30,000 letters of the virus version that infected each person.
So far in the pandemic, experts have observed that SARS-CoV-2 accumulates one to two mutations per month, explains Villabona.
Genomic surveillance should review the 30,000 letters of the virus that infects each person and note what changes have occurred in relation to other people’s viruses.
“Genomic (surveillance) is the only technology that allows us to identify the new variants that concern us,” says BBC News Mundo Catalina López Correa, a medical specialist in genetics and executive director of the Canadian Genomic Network of Covid-19 (CanCOGeN).
“If we don’t understand what variants we have and how they are being transmitted, we run the risk that at some point the vaccines will not be effective.”
In turn, Villabona adds that “genomic surveillance allows us to be careful that the virus does not change in a way that complicates the situation and that, if it is changing, strategies can be activated to reduce its impact”.
The equation is clear: the greater the number of variants, it is possible that the number of infections will increase; and the greater the number of infections, the greater the likelihood of new variants appearing.
Surveillance in Latin America
Genomic surveillance of SARS-CoV-2 in Latin America “is in an embryonic state”, in the words of López Correa.
The expert comments that the United Kingdom, for example, registered about 300 thousand genomes of the virus in GISAID. Canada inserted more than 22 thousand.
As of March 22, Latin America and the Caribbean as a whole had registered less than 14,000, according to the Regional Genomic Surveillance Network of covid-19, which is supported by the Pan American Health Organization (PAHO).
As of March 31, GISAID had more than 940,000 SARS-CoV-2 strings on its global platform.
López Correa points out that, in Latin America, countries like Mexico and Brazil lead the number of sequences registered, and that in Colombia, Peru and Ecuador the number of reported genomes is increasing little by little.
The expert warns, however, that “we are going slow”.
“I think that in Latin America we are not being very aware of the importance of genomic surveillance.”
Villabona says, in turn, that the number of genomes registered in Latin America is very low compared to the total number of cases of covid-19 in the region, which is around 24 million.
“In Latin America, there is a possibility that there are variants that have not been registered and that are responsible for a significant fraction of the cases,” he explains.
“We cannot know, because the genetic data does not exist … with that number of sequences that we have, it cannot be calculated.”
At a press conference on March 23, PAHO said it is supporting Latin American countries to strengthen their virus surveillance capacity, and that one of its main objectives is to expand this screening network with new laboratories, financing and technical assistance.
Experts agree that Latin America has people trained to do more genomic surveillance.
López Correa says, however, that “resources and prioritization from a strategic and political point of view are lacking”.
The expert points out that genomic surveillance is an important tool for making public health decisions, such as imposing lockdowns, for example.
“Right now, vaccination and surveillance are equally important,” he warns.
According to Villabona, Latin America has so far focused on monitoring whether a variant from another region is present, but a greater effort should be made to find out if a variant from the continent itself has the same effect.
In Brazil, for example, it was important that a genomic surveillance program for viruses such as dengue, zika or yellow fever was created some years ago.
As Villabona explains, because this infrastructure already exists, it was possible to adapt it to track the coronavirus genome.
Finally, although experts insist that the governments of each country prioritize genomic sequencing at the national level, surveillance must be seen as a matter of global cooperation.
If a country does not adequately monitor possible variants of the virus, it could become a worldwide public health problem.
“For the virus, there are no borders,” concludes López Correa.
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