Like all viruses, the new coronavirus that causes Covid-19 mutates over time by requisitioning the cells of people it infects to make copies of itself.
Versions of the virus that inherit shared sets of mutations or variants emerge. Some are disappearing. Others continue and raise concerns because of their infectiousness, severity or potential to evade immune defenses.
Three of these variants, one first appeared in Britain in September, another identified in South Africa in December and a third detected around the same time in Japan and Brazil, raise such concerns. . All three variants contain mutations in the so-called spike protein on the surface of the coronavirus that help them bind better to cells in our nose, mouth, and lungs. This increases their chances of infecting someone and makes the variants more contagious.
“Every time the virus copies itself, it’s like a game of chance,” says Dr. Taison Bell, intensive care physician and director of the University of Virginia medical intensive care unit. “Sometimes when he plays and changes on his own it doesn’t make much of a difference in the virus, but sometimes he hits the jackpot, and he finds a change that either allows him to spread or be more deadly. . “
Variant B.1.17 (UK)
The so-called British variant, known as B.1.17, carries eight mutations in the spike protein. One, known as N501Y, reshapes the tip of the tip to more closely adapt to receptors in a human cell. Another, known as the 69/70 deletion because it removes some amino acids from the spike, helps the virus tighten its grip on cells it can infect. Taken together, the mutations mean that smaller amounts of the virus can cause infection, leading to even more people getting sick.
B.1.17, which is around 50% more infectious than earlier variants, quickly became the dominant infection strain in the UK and has since been reported in 114 countries. The variant may increase the severity of illness due to Covid-19 but does not significantly decrease the effectiveness of vaccines.
Variant B.1.351 (South Africa)
B.1.351, as the variant discovered in South Africa is known, shares the N501Y mutation with B.1.17. This makes B.1.351 about 50% more contagious than the previous variants. Since its first occurrence, B.1.351 has been reported in at least 67 countries. The variant carries nine mutations at its peak, including one known as E484K which helps the variant bypass immune defenses.
While there is no evidence that B.1.351 increases disease severity, the variant reduces protection from current vaccines and may re-infect people who have recovered from Covid-19 caused by previous variants. In February, South Africa put aside plans to roll out the Covid-19 vaccine developed by AstraZeneca and the University of Oxford after preliminary studies suggested the vaccine offered insufficient protection against the disease caused by B.1.351, which represents most of the cases in this country.
Variant P.1 (Brazil)
P.1, as the variant first detected in Japan and Brazil is known, shares several mutations with B.1.351, including the N501Y and E484K mutations, as well as a mutation known as K417T, which resembles to a key peak mutation in the B .1.351 variant. Taken together, the collection of mutations makes the P.1 variant up to 2.2 times more contagious than earlier variants thanks to its ability to lock more tightly to human cells.
Although the variant, which has been reported in 36 countries, does not appear to cause more severe disease, it can elude 61% of the immunity generated by infection with previous strains. The variant reduces the effectiveness of vaccines developed by Pfizer, BioNTech and Moderna, although both injections appear to protect against serious illness.
The more the new coronavirus spreads, the more variants will emerge. The prospect that some might unravel due to their infectiousness or potency underscores the urgency of ensuring that vaccinations reach the arms of billions of people around the world. “We need to reduce the chances of the virus hitting the jackpot, through public health measures that keep the virus at low levels, and getting widespread immunizations,” says Dr Bell.