February 25, 2021

It is not yet known why the British strain of COVID-19 could be more lethal


Those who have been comforted in recent weeks by the evolutionary theory of viruses, according to which mutations that make them more contagious also make them less lethal, may now be pondering the news of the Kent-originated variant: not only it spreads more easily, but could also kill more people.

During the press conference in Downing Street, the British government’s chief scientific adviser, Sir Patrick Vallance, said that in people over 60 with the new variant, the number of deaths per 1000 cases of COVID-19 could be 13 or 14, instead of the 10 deaths per 1000 cases that had been registered so far. The reasons for this increased fatality have not yet been clarified.

The theory of the balance between lethality and ease of contagion is based on the way viruses survive: if they are too lethal, they kill their hosts. So when a virus begins to spread more, the lethality is lower. If not, there would be no one left to infect.

SARS-CoV-2 has a way to avoid this problem and that is to spread it to people before they know they are sick. Any carrier of the virus can walk around feeling perfectly fine and infecting others. Transmission to other people has already occurred when he finally enters the hospital and is fighting for his life on a ventilator.

According to Professor Deenan Pillay, a virologist at University College London, “the fact that people die is almost like a side effect.”

One reason that could explain what is happening is that the greater ease of transmission observed in the virus is due to a higher viral load, that is, that people have more virus in their respiratory system. “If that’s the mechanism, presumably having more viruses replicating there would be a correlation with a worsening of the disease,” Pillay explained. He also said that until now it had not been documented that this was what was happening.

Vallance does not believe it is attributable to a higher viral load. In their opinion, it is possible that the new variant binds more firmly to the receptor and enters cells more easily or grows with less difficulty in certain types of cells.

Clearly, there is a lot of work to be done before obtaining reliable answers and there may not be enough information yet. Pillay explained that the results obtained came from tests done on people in the community. These are not people in the hospital with the disease in serious condition, so the sample size of those who die is smaller.

Without a doubt, this discovery is going to make other countries close the doors to people who want to travel from the UK. According to Pillay, that’s the right thing to do. Border control has worked well in many places, such as Australia and New Zealand.

In fact, what this means is that we must implement all the measures that we already know to control the virus. There is no new mechanism to deal with it. What the increased fatality implies is that we have to try even harder not to get infected. Pillay notes that the first containment measures were more restrictive and respected than the current ones. For starters, there is now more mobility.

The news puts more weight on hopes of mass vaccination as a way to get out of our predicament, although even those hopes now seem more uncertain. It has been suggested that the vaccines we are using now might be less effective with the variants originally found in South Africa and Brazil.

The Daily Mail newspaper published remarks that were apparently made by Health Secretary Matt Hancock during a webinar for travel agents. He said there was “evidence in the public domain” that the South African variant reduced the efficacy of the vaccine by “about 50%.” Although he then added: “We are not sure about this data, so I would not say it in public.

The good news is that vaccine manufacturers have consistently claimed that they can modify vaccines to cope with the variants, and there are signs that right now they are looking at whether and how they can.

Translated by Francisco de Zárate.

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