In 1960 researchers from the United States and the United Kingdom isolated two viruses that cause common colds in humans and that under the electron microscope they looked like solar crowns in its molecular structure, which led the researchers in 1968 to coin the term coronavirus.
For many years scientists thought that coronaviruses only caused mild symptoms in humans, until the outbreak of severe acute respiratory syndrome (SARS) that emerged in China in 2002 revealed the ease with which these versatile respiratory viruses could spread and kill people.
As humanity faces the new pandemic and the number of deaths and infections increases by hundreds of thousands every day due to COVID-19 (95 million infected and more than 2 million deaths are already counted) researchers strive to discover the biology of the latest coronavirus, which has developed a series of adaptations that make it much more contagious and also lethal than the other coronaviruses that humanity has known so far.
Unlike his close relatives, SARS-CoV-2 can easily attack and penetrate human cells at multiple points, with the lungs and throat being the main targets. Once inside the body, the virus uses a diverse arsenal of dangerous molecules to duplicate itself and display its viral load.
The danger of mutations
“It is not the strongest species that survives, nor is it the most intelligent that survives. It is the one that is more adaptable to change“, Said with great wisdom the British naturalist Charles Darwin, recognized for being the most influential scientist of those who raised the idea of biological evolution through natural selection, justifying it in his work” The Origin of Species “. Those wise words also adapt to the behavior of viruses.
In the vast battlefield that is nature, all viruses naturally mutate to survive. “Changes in nature are random and always seek to prevail over time and survive. Any species changes its genetic makeup over time. Thus, neutral, negative or positive changes occur (efficient when reproducing). This is how natural selection works. Everything in biology is genes and the developing environment ”, he explained to Infobae biologist and doctor of science Federico Prada.
“And why was it so effective and lethal in humans? Because the SARS-CoV-2 virus has one of the most important biological characteristics such as key entry to the human body: the molecule angiotensin converting enzyme 2 (or ACE 2), which is present to a large extent in our body such as lungs, kidneys and intestines. Then the virus enters the organism infecting cells and duplicating itself in its genetic material with the aim of dividing and generating more copies ”, added the director of the Bioinformatics degree and the Biotechnology degree of the Argentine University of the Company (UADE).
And he specified: “The virus has a compressed genome. If we look at it from a literary point of view, Viruses are authors of genomes that can tell a story in a nutshell. A lot of information in a small space. And each organism that infects is a large laboratory where one, two or more mutations can occur ”. A more contagious SARS-CoV-2 virus is certainly also more lethal. Not because it makes any individual sick, but because it reaches more people. More disease means more cases: more mild cases, more severe cases, more long-term complications, more hospitalizations, and ultimately more deaths.
Scientists still don’t have a perfect estimate of how much more contagious the SARS-CoV-2 variant called B.1.1.7, which was first discovered in the UK, could be. To determine this, more extensive laboratory work is needed in animals, which could take a few more weeks. But preliminary estimates find that it is up to 70 percent more contagious than the Wuhan-originated coronavirus., China at the end of 2019. This variant, which has already arrived in Argentina, as confirmed by scientists from the ANLIS-Malbrán laboratory, is spreading throughout the world along with other new mutations found, such as the 501Y.V2 variant that was found by first time in South Africa or the recent call Rio de Janeiro (B.1.1.28).
“One of the best ways to know an organism is to sequence its genome, It contains the necessary instructions to make it work. When a pandemic like COVID-19 occurs, knowing the genome of the responsible infectious agent provides highly relevant information for researchers. It allows them to identify what causes the disease, to know its origin and evolution over time, or to develop therapeutic strategies to deal with it ”, stated the scientific-technical director of the Malbrán Institute. Claudia Perandones (MN 83,079).
Why is it key to sequence and know the genetics of the circulating virus? “It is essential to carry out genomic sequencing of all adenoviruses that circulate both nationally and regionally, to guarantee the effectiveness of protection through vaccination “says Perandones.
The danger of more deaths
Regardless of how transmissible exactly the new variants are, Any possible increase in transmissibility is extremely worrying to epidemiologists and other public health professionals. It means that now, more than ever, our collective and individual actions to stop the spread are critically important. And the individual responsibility to take extreme care of oneself, with behaviors recommended by experts such as social distancing, the use of a mask, frequent hand washing and not staying indoors for a long time with many people.
The reason for concern for a more contagious variant of the virus is simple. “Once [la variante] becomes common, it will speed up transmission considerably. Accelerated transmission means more cases“Said Harvard epidemiologist Marc Lipsitch. That is because the virus grows exponentially. Any increase in its inherent transmissibility causes an increasing number of cases in the future.
With a 50 percent increase in infectivity, “in less than two weeks, the number of cases doubles. And in a month or so, you have four, five times more cases or more“Lipsitch pointed out. Epidemiologists think of the transmissibility of a virus with a number called R, or the basic reproduction number. This describes how many new cases, on average, will follow a case of the virus.
At the beginning of the outbreak epidemiologists estimated the R to be around 2 or 3. Since then, thanks to our efforts (implemented inconsistently) such as wearing masks, social distancing, business closings, etc. R has been lowered, but as long as the R figure is greater than 1, the virus can spread exponentially. If a community lowers its R-value to 1, but a 50 percent more transmissible variant appears, the same mitigation effort that reduced the old virus variant to 1 now only reduces it to 1.5. In other words, to combat a more transmissible version of the virus, communities need even stricter controls. “50 percent more transmittable virus means that reducing our contacts by another third compared to the already strong restrictions in place to be able to return to the same place where we were,” said the expert.
“If communities do nothing about a more contagious variant, the numbers could add up very quickly“Added Bill Hanage, another Harvard epidemiologist, who communicated with an example the danger of a more contagious variant. “Let’s say a community has the virus more or less under control. The R value in the area is 1, which means that the number of cases in the area remains constant, month to month. In this scenario, you now have 1000 cases and will have 1000 cases within a month, ”says Hanage, who estimates one scenario assumes that it takes about five days for one infection to cause another). “Now let’s imagine that the virus is 50 percent more transmissible. With 1000 cases of a virus of this type now it would translate into more than 10,000 within a month if you did nothing, “he warned.
A more transmissible virus increases the number of people who need to be vaccinated
When a more transmissible virus appears, the threshold for herd immunity also increases, or the rough estimate of the percentage of people in a population who need to achieve immunity, ideally through a vaccine, for the outbreak to decrease in size.
Herd immunity thresholds depend on the value of R. The higher the value of R, the higher the threshold. If a more transmissible variant becomes dominant around the world, the pressure on vaccination campaigns to vaccinate even more people increases. Experts say that more than 70 percent of the population will need to be immune to the new coronavirus to achieve herd immunity, which is really a huge challenge given the slow early delivery of vaccines that occurs today. There is also the danger that the virus could mutate in a way that reduces the effectiveness of current vaccines.
A more transmissible virus means more death
London School of Hygiene & Tropical Medicine epidemiologist, Adam Kucharski, explained that a A virus that is 50 percent more contagious is a bigger concern than one that is 50 percent more lethal. “If a city has an R-value of 1.1 and there are 10,000 people infected, in a month, you would expect to see 129 deaths. But increasing the lethality of the virus by 50 percent in that scenario implies having 193 deaths, that is, an increase of 49.6 percent. And increasing the spread of the virus in this scenario by 50 percent will ultimately result in 978 deaths, that is, an increase of 658 percent. If there is a theoretical calculation, the central point is the dangerous exponential effect of a new, more contagious strain, “added Kucharski.
There is a simple solution so that no more mutations happen. And it is stop the spread of SARS-CoV-2 in general. Something as simple to imagine as difficult to do.
Infographics: Marcelo Regalado