The two new strains of SARS-Cov-2, one of which has emerged in the UK and the other in South Africa, are wreaking havoc at the start of a new year that seemed to be in good hands with the start of vaccination campaigns. The international scientific community is concerned that both strains are more contagious, and the British are very worried right now.
The New Strains
The emergence of two new variants of SARS-Cov-2 in the UK and South Africa, which initial data suggest are more contagious, is of great concern to the international community. Let’s take stock of these two changes. First, what are these new strains? All viruses mutate. These mutations are changes that occur during replication. Scientists have observed several mutations since SARS-Cov-2 first appeared, most of which are inconsequential, but some may give it a survival advantage, including increased transmissibility.
The B.1.1.7 variant discovered in the U.K. in November, now called VOC 202012/01, probably originated in southeast England in September, according to Imperial College London. It has spread rapidly in the U.K. and has since been detected in dozens of countries around the world, from the United States to South Korea, India, France, and Denmark.
The extent of spread Probably underestimated
Most of these cases are linked to the United Kingdom, but in a few cases, no link to the United Kingdom could be found, showing that the variant has already become established locally. This has occurred in Denmark, one of the countries with the most cases so far, where 86 cases were identified.
Another strain, called 501.V2, is now the cause of the majority of new infections in South Africa. It has been detected in samples dating back to October and has been identified in several other countries around the world, including the United Kingdom. Experts believe the number of cases of both variants is likely underestimated.
Two highly transmissible strains
These two variants have several mutations, one of which, called N501Y, is the focus of interest. It is located in the coronavirus spike protein, a spike on its surface that allows it to adhere to and enter the ACE2 receptor on human cells, and therefore plays a key role in viral infection.
This N501Y mutation is known to increase the virus’s ability to bind to the ACE2 receptors. “There is no clear link between ACE2 binding and increased transmissibility, but it is plausible that such a link exists,” says the European Centre for Disease Prevention and Control (ECDC).
Several scientific studies that have not yet been peer-reviewed and are based mainly on modelings conclude that the British variant is significantly more transmissible. This confirms the initial estimates of the NERVTAG research group which advises the British government, which assumes a 50-70% increase in transmission. Thus, according to calculations by the London School of Hygiene and Tropical Medicine (LSHTM), the British variant could be 50-74% more contagious.
The first studies on the British strain also showed that young people under 20 are more infected by this new strain.
In their latest report, published Thursday, researchers at Imperial College London analyzed thousands of genomes of SARS-Cov-2 viruses sequenced between October and December. Using two different methods, they concluded that this variant has a significant advantage in terms of contagion: 50% to 75% more contagious, or a viral replication rate (R) between 0.4 and 0.7 higher than that of the common strain.
Preliminary results for the South African variant also suggest increased transmissibility, but not enough data are available. However, some experts believe there are not enough data to assess the contagiousness of the two strains with certainty.
Why is it more problematic?
“There is no information on whether infections with these strains are more serious,” ECDC says. But the risk “in terms of hospitalizations and deaths is high.”
Higher transmissibility can mean much higher incidence and therefore, even with the same lethality, more pressure on the health system. A variant of SARS-CoV-2 that is “50% more transmissible would be a much bigger problem than a 50% more lethal variant,” asserts UK epidemiologist Adam Kucharski on Twitter, citing statistical evidence.
With a reproduction rate of 1.1, a mortality rate of 0.8%, and 10,000 people infected, this would result in 129 deaths after one month, he explains. If the mortality rate increases by 50%, the number of deaths would rise to 193. However, if the transmission rate increases by 50%, there would be 978 deaths. The impact would be particularly significant in countries where even a small increase in transmissibility would drive the reproduction rate above 1, accelerating the epidemic. Clearly, a 50% more transmissible variant of SARS-Cov-2 would be a much bigger problem than a 50% more lethal strain.
The British variant is “really the worry of the moment because it can plunge us into an extremely complex situation,” epidemiologist Arnaud Fontanet, a member of the scientific council that advises the French government, warned on France Info radio Monday. In addition, the first studies on the British strain show increased infection of young people under 20, which raises the question of whether to open schools. Thus, the LSHTM study believes that restrictive measures such as containment, which was implemented in the U.K. in November, would not be sufficiently effective in controlling the epidemic “unless schools, colleges, and universities are also closed.”
Vaccine effectiveness not in question
While the vaccination campaigns just getting underway offer hope for a way out of this global health crisis, some question the vaccines’ ability to combat new strains. For both variants, “there is insufficient information at this stage to assess whether they pose a risk to vaccine efficacy,” the ECDC said.
However, “based on the current state of our knowledge, experts believe that the current vaccines are effective against these strains,” Henry Walke of the U.S. Centers for Disease Control and Prevention said at a press conference Wednesday. German lab BioNTech, which with Pfizer originally developed the world’s first approved Covid-19 vaccine, assured Walke that it could provide a new vaccine “in six weeks” if needed to respond to a mutation.
Individual and collective vigilance is needed
It is highly unlikely that we can eradicate or completely prevent the spread of new variants. Therefore, for countries where cases of new variants are not widespread, ECDC recommends “similar efforts to stop the spread as were undertaken at the beginning of the epidemic”: testing people arriving from risk areas, with possible quarantine, isolation and better contact tracing of infected people, restriction of travel, etc.
There is also a need to monitor the emergence of these variants, especially through enhanced sequencing of the viruses. Some PCR tests can also give an indication of the presence of the British variant and then better target the sequences, explained Professor Fontanet, who believes that extremely aggressive surveillance is essential.
On an individual level, “since these variants seem to spread more easily, we need to be even more vigilant in our prevention measures to stop the spread of Covid-19,” Dr. Walke emphasized, referring to the use of masks, physical distancing, hand washing, and ventilation of enclosed spaces, not to mention avoiding crowds.