A new strain of coronavirus detected in the UK and spreading across southern England is touted as ‘highly contagious’, resulting in a strict lockdown of the country over the Christmas holidays. The variant, first identified in September, is being closely watched by scientists and researchers, in an effort to understand whether it is more infectious or transmissible than previous variants.
Cases of the variant, dubbed VUI 202012/01 (for ‘variant under investigation’), have grown rapidly over the past month, which has led to increased surveillance by UK authorities. It has also been reported from the Netherlands, Denmark, Belgium and Australia. A preliminary study of the new strain shows that it has an unusually high number of 17 mutations in its genetic code, some of which can change key characteristics.
However, it is not known whether this mutant variant of the coronavirus is more transmissible based solely on these genetic variations. “We cannot tell from the footage that [the] A set of mutations will provide better transmissibility, ”says Ian Mackay, virologist at the University of Queensland, Australia.
British Prime Minister Boris Johnson said on Saturday that “when the virus changes its method of attack, we must change our method of defense” but this, perhaps, exaggerates the capabilities of the new strain, which we still know about very little. One of the main models of epidemiology is the “triad” which postulates that diseases are spread by the infectious agent, the host and the environment. “When you get a quick climb [of cases], all three things contribute, ”says Catherine Bennett, Chair of Epidemiology at Deakin University, Australia.
It could be that the variant’s genetic mutations improved its ability to move from person to person, or it could be a combination of increased movement and bad luck. Scientists will spend the next few weeks trying to unravel this mystery. Investigations begin with the spike protein.
Viruses are constantly changing. They are mutating. These small changes in their genes sometimes provide a survival advantage or increase the “physical form” of the virus. The coronavirus, SARS-CoV-2, is no different. This is not of concern and is not unexpected – thousands of mutations have occurred since the SARS-CoV-2 genome was sequenced in January.
“It constantly mutates as it passes through people,” Mackay says.
Think of the virus’s genetic code as a copy of Harry Potter and the Sorcerer’s Stone and your cells as photocopiers. The virus wants to make millions of copies of Harry Potter. Every time he hijacks a cell, he’s making copy after copy of Harry Potter. But this process is prone to errors. Sometimes entire pages are missing. Other times, pages are duplicated or whole new pages are added. Most of the time, that doesn’t really change the story. Occasionally that changes him completely.
Since the start of the pandemic, scientists have focused on one particular aspect of the history of SARS-CoV-2: the club-shaped spikes affixed to the shell of the virus. This is the peak that allows the virus to hijack human cells. If we stick to the Harry Potter analogy here, then the peak’s genetic code is like an entire chapter.
In VUI 202012/01, this chapter reads differently.
The new variant has eight mutations in the spike gene, including one known as N501Y, which changes the efficiency with which SARS-CoV-2 adheres to human cells. In mice, this particular mutation has been shown to make the virus more infectious, and in South Africa this mutation in combination with a variety of others is associated with an increasing number of cases. Another mutation, 69-70del, has already been seen in other coronavirus variants and has been linked to a mink-related epidemic in Denmark.
X amount of luck
In his speech on Saturday, Boris Johnson suggested that the variant “could be up to 70% more transmissible than the old variant” based on early analysis by the UK’s Advisory Group on New Respiratory Virus Threats and emerging (NERVTAG). The data behind this figure has yet to be released and is based on computer modeling.
But other scientists suggest that the growing incidence in the UK may simply be due to a confluence of circumstances – luck or chance – rather than changes in the viral genome.
“Any apparent increase in transmission now could also be due to human behavior during the Christmas season and the increase in movement and social contact associated with it,” says Raina MacIntyre, professor of global biosecurity at the Kirby Institute. from the University of New South Wales.
In November, talks about a “particularly devious strain” in Adelaide, South Australia, put the state on lockdown. One cluster of cases appeared to show the virus spreading faster, but later evidence suggested it was no longer infectious or transmissible.
“It could be just another Adelaide event,” says Stuart Turville, an immunovirologist at the Kirby Institute. But, he says, the answers won’t come until scientists have had a chance to test the new variant in the lab, compare it to previous variants, and see how it fares. “Until you get to this point, you can’t really tell the virus is any healthier. ”
The origin of this variant is still unknown, although NERVTAG suggests that it may have appeared in a single patient with a weakened immune system over a period of several months. Inside the patient, the virus and the immune system are in a constant arms race, trying to outdo each other and gain the upper hand. In this environment, there is more pressure to mutate. The persistent battle means “there is a higher probability” of mutations building up in the patient, Turville says.
The number of changes in VUI 202012/01 will challenge researchers to explain whether a single mutation or a combination of these contributes to the spread of this variant or to its severity. “Because there are so many different changes, it’s going to be hard to really put in place,” says Turville.
Researchers will assess these changes through a series of experiments that Turville notes could take up to a few weeks. To test if the variant is more transmissible, they compare it to older strains in human cells in the lab or in animal models and see which one dominates.
Transmissibility, however, is only the tip of the viral iceberg.
“The types of mutations that scientists are more concerned about are those that bypass vaccines, antibodies, therapies – rather than increased transmissibility,” says Alina Chan, a scientist at the Broad Institute at MIT and Harvard.
This assessment requires a different type of test. Scientists hit the variant with antibodies created by people infected with older versions of the coronavirus. If the antibodies prevent the variant from growing, so much the better – but if the mutations in the variant help it escape the antibodies, we may be dealing with an offshoot that could bypass some of our defenses.
As scientists and researchers separate VUI 202012/01 and determine how its genetic mutations may have altered it, the message remains the same. “There really is nothing that can be done differently, in terms of public health,” Chan says. Social distancing and wearing a mask remain essential to slow the spread of COVID-19. These measures are the gold standard and will continue to work against the new variant.
It is too early to say how the new variant might change our public health message or if it will raise concerns for the vaccines being deployed around the world. Experts say increased surveillance will be important, but our vaccines will not be rendered useless overnight.
“We’re a long way from a mutation here or a variant there, which makes us really worried that our vaccine will drop,” Mackay says.