The six strains of COVID-19

COVID-19

The virus causing the coronavirus pandemic, SARS-CoV-2, presents at least six strains.

Across Europe and Italy, the most widespread is strain G, while the L strain from Wuhan, China, is gradually disappearing, according to researchers from the University of Bologna, Italy, ScienceDaily reported.

The researchers performed the most extensive study out on SARS-CoV-2 sequencing, drawing from the analysis of 48,635 coronavirus genomes, which were isolated by researchers in laboratories all over the world. It was then possible for researchers to map the spread and the mutations of the virus during its journey to all continents.

The virus has infected more than 20,500,000 people across the world, officially killing 746,000 people, although the true figures are likely to be much higher. The 10 countries with the highest death tolls on Tuesday were the US (1,504), Brazil (1,242), India (835), Mexico (705), Columbia (321), Argentina (240), Peru (225), Iran (184), Russia (130) and South Africa (130).

SARS-CoV-2
The cases and deaths from COVID-19 continue to rise. Supplied: Worldometer

“The SARS-CoV-2 coronavirus is presumably already optimized to affect human beings, and this explains its low evolutionary change,” said Federico Giorgi, a researcher at the University of Bologna and study coordinator. “This means that the treatments we are developing, including a vaccine, might be effective against all the virus strains.”

Currently, there are six strains of coronavirus. The original one is the L strain, that appeared in Wuhan, China, in December 2019. Its first mutation, the S strain, appeared at the beginning of 2020, while, since mid-January 2020, we have had strains V and G. To date strain G is the most widespread: it mutated into strains GR and GH at the end of February 2020.

“Strain G and its related strains GR and GH are by far the most widespread, representing 74% of all gene sequences we analysed,” said Giorgi. “They present four mutations, two of which are able to change the sequence of the RNA polymerase and Spike proteins of the virus. This characteristic probably facilitates the spread of the virus.”

Strains G and GR are the most frequent across Europe and Italy. Available data shows GH strain seems close to non-existence in Italy, while it occurs more frequently in France and Germany. This appears to confirm the effectiveness of containment methods in Italy.

In North America, the most widespread strain is GH, while in South America we find the GR strain more frequently. In Asia, where the Wuhan L strain initially appeared, the spread of strains G, GH and GR is increasing. These strains landed in Asia only at the beginning of March, more than a month after their spread in Europe.

Globally, strains G, GH and GR are constantly increasing. Strain S can be found in some restricted areas in the US and Spain. The L and V strains are gradually disappearing.

Besides these six main coronavirus strains, researchers identified some infrequent mutations, that, at the moment, are not worrying but should nevertheless be monitored.

“Rare genomic mutations are less than 1% of all sequenced genomes,” said Giorgi. “However, it is fundamental that we study and analyse them so that we can identify their function and monitor their spread. All countries should contribute to the cause by giving access to data about the virus genome sequences.”

This study was published in the journal Frontiers in Microbiology.

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