Since the start of the pandemic, there have been concerns that the聽coronavirus could evolve to become more dangerous. Now, hospitals in the UK are at risk of being overwhelmed by surging numbers of covid-19 cases and there is growing evidence that this is partly due to a new variant of the virus that spreads more readily. This variant has already reached many other countries.
Hospitals in South Africa are聽also being overrun, due to a聽resurgence of covid-19 being blamed on another variant of SARS-CoV-2, the virus responsible.
It isn鈥檛 yet clear how much faster this variant, called B.1.351, spreads. Yet initial studies of the variant from the UK, known as B.1.1.7, estimate that it is around 40 to 74 per cent more transmissible. This may be because people infected with it shed more of the virus.
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In response to these initial studies and high UK transmission rates, England and Scotland this week joined Wales and Northern Ireland in another period of strict lockdown, during which most schools and universities will use remote learning.
鈥淣o matter how the virus changes, it needs us to be close enough to each other and to have interactions to let it jump between us,鈥� says Emma Hodcroft at the University of Basel in Switzerland. 鈥淚f we don鈥檛 give the virus those opportunities, it simply can鈥檛 spread no matter what variant it is.鈥�
Neither new variant appears any deadlier. But there is concern that current vaccines could be less effective against B.1.351.
The new variants were discovered by sequencing the entire genome of the virus, which is around 30,000 RNA letters long. Researchers around the world routinely sequence samples to track the spread of the coronavirus and see how it is evolving.
Such efforts have found there are already tens of thousands of聽鈥渕utant鈥� viruses that differ from each other by at least one mutation. This is unsurprising as聽viruses constantly mutate.
In fact, the coronavirus changes less than many other viruses. Any聽two SARS-CoV-2 viruses from anywhere in the world will usually differ by fewer than 30聽mutations, and they are regarded as all belonging to the same strain. Researchers instead talk about different lineages or variants.
B.1.1.7 was first sequenced in the聽UK on 20 September. It caught the attention of scientists on 8聽December, when they were looking for reasons for the surge of cases in south-east England.
B.1.1.7 has 23 mutations compared with the original SARS鈥慍oV-2 virus first discovered in Wuhan, China. Seventeen lead聽to changes in viral proteins. Many of these mutations have been found before and their overall number isn鈥檛 unusual, but聽this combination is unique.
In particular, eight of the mutations in B.1.1.7 change the shape of the outer spike protein. One of these mutations, called N501Y, is in the part of the spike protein that binds to receptors protruding from human cells and helps the virus infect them聽鈥� the receptor binding domain.
The N501Y mutation might help make the virus more infectious by binding more tightly to the human receptors. However, this can鈥檛 be the whole story, as this mutation has been around for a while. It was first seen in Brazil in April and has since been detected in several other countries with no apparent effect on transmission.
So if B.1.1.7 is more infectious, it must be due to a combination of mutations. Lab studies are under way to try to understand the effects of its mutations, but, for now, the main evidence of higher transmissibility comes from the fact that it is spreading faster than other, older variants.
Normally, the only way to truly聽tell if one particular variant is聽spreading faster than others is to sequence entire viruses. But in one way, health authorities in the UK got lucky. The standard test for the coronavirus involves looking for any of three small parts of the viral genome. By chance, in some tests used in the UK, one of these parts is the region where one of the mutations in B.1.1.7 occurs, causing this element of the test to produce a negative result with the variant.
So by looking at standard test results that came back positive for only two of the three parts, called an S聽gene dropout, we have been able to get a better idea of how fast聽the variant is spreading in the UK than would be possible from genome sequence data alone.
Based on this, 聽by Neil Ferguson at Imperial College London and his colleagues concludes that B.1.1.7 has 鈥渁 substantial transmission advantage鈥�, spreading 40 to 70 per cent faster than other variants.
Another , by Nick Davies at the London School of Hygiene &聽Tropical Medicine and his colleagues, put B.1.1.7鈥檚 increased transmissibility at 50 to 74 per cent.
also add to the evidence that B.1.1.7 spreads faster. So far, only 86 cases of the variant have been detected in Denmark. However, the percentage of B.1.1.7 in sequenced samples has risen every week for the past four weeks.
Meanwhile, a study of 600 nose or throat swabs by Michael Kidd at聽Public Health England鈥檚 public health laboratory in Birmingham and his colleagues found of S gene-dropout samples聽鈥� that is, ones from people who probably had B.1.1.7聽鈥� compared with 10 per cent of samples without S gene dropout. This suggests that B.1.1.7 is more infectious because people shed more viruses on average, but this聽has yet to be confirmed.
All this is bad news because it聽means tougher measures are needed. 鈥淲ithout effective control policies, rapid surges are predicted and the burden in the first six months of 2021 may be greater than what was seen in 2020,鈥� before Christmas about the threat posed to England.
Early data suggested that B.1.1.7 might spread especially readily among children. It now appears that this was just an artefact related to schools being open during the second lockdown in England in November, .
Nonetheless, his analysis suggests that imposing a similar lockdown won鈥檛 be enough to stop B.1.1.7. It will be necessary to close schools and universities too, as has largely happened in the UK.
The good news is that an initial found that people infected with B.1.1.7 were no more likely to be hospitalised or to die than those infected with other variants.
The B.1.351 variant in South Africa also seems to cause higher transmission rates. In October, coronavirus cases began rising unusually fast in Nelson Mandela聽Bay Municipality. They聽soon started rising fast in聽surrounding areas too.
This prompted the sequencing of thousands of viral genomes to聽see if a new variant had arisen. That revealed the B.1.351 lineage, which, when first sequenced on 15聽October, had various mutations including six in the spike protein. By the end of November, it had acquired another three in the spike protein. Only one of the mutations, the N501Y one, is the聽same as in B.1.1.7.
What is worrying some researchers is that B.1.351 has three mutations, including N501Y, in the receptor binding domain of the spike protein. This is an important region for immunity as well as infectivity because many of our antibodies work by attaching themselves to this region.
This might mean that vaccines confer less protection against B.1.351 than they do against other variants, but we just don鈥檛 know yet. 鈥淚t鈥檚 all speculation still,鈥� says 脕ine O鈥橳oole at the University of聽Edinburgh, UK. 鈥淲e have no confirmation.鈥�
Lab studies are now under way to try to find out, for instance by measuring how well antibodies from people who have been vaccinated bind to these variants.
Meanwhile, other countries are trying to avoid importing the new variants, but it may be too late. B.1.351 has reached at least eight countries besides South Africa, including the UK and Australia, although it isn鈥檛 reported to be spreading locally, says O鈥橳oole, who is part of a team .
B.1.1.7 has reached at least 39聽countries, including the US, China, Australia and New Zealand, and is definitely spreading locally in a few. So far, Denmark has reported the most cases besides the UK, but this is likely to be because it does more sequencing than most other countries.
More people from the UK travel to countries such as Spain and Germany than Denmark, O鈥橳oole points out, so the expectation is that there should be more cases of聽B.1.1.7 in these places. 鈥淭he virus moves with people,鈥� she says.
Both O鈥橳oole and Hodcroft think other nations should do all聽they can to prevent more introductions of this new variant. This will help keep down the number of cases and make them easier to control, says Hodcroft. 鈥淭he goal here is more to buy time,鈥� she says.
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