三个主要问题将决定 Covid 病毒的新 Omicron 变体对美国和地球其他地区的影响程度. 这种新的 Covid 变体的传播性如何? How good is it at evading the antibodies and T-cells that make up a person’s immune defences? What are the chances it will trigger severe illness that could lead to the hospitalisation, and possibly death, of an infected person.
Scientists are struggling to find definitive answers to these critically important questions, although evidence already suggests Omicron has the potential to cause serious disruption. “The situation is very finely tuned and could go in many different directions,” says Prof Rowland Kao of Edinburgh University.
The Omicron variant has now been detected in 38 国家, although no deaths have yet been reported in any of these nations, 根据 世界卫生组织. 这 我们 和 澳大利亚 have become the latest countries to confirm locally transmitted – as opposed to imported – cases of the variant. 在周五, the UK Health Security Agency announced that 75 more cases of the Covid-19 Omicron variant had been identified in England, bringing the total number of confirmed cases to 104.
As a result of Omicron, many nations that were already suffering from soaring numbers of Covid-19 cases caused by the Delta variant have imposed new lockdown measures and travel restrictions.
Omicron has spread rapidly in 南非, to the alarm of researchers worldwide. 在 1 十二月, 记录的国家 8,561 cases compared with a total of 3,402 reported on 26 十一月. In mid-November, only a few hundred cases were noted. South Africa’s National Institute for Communicable Diseases (NICD) in Johannesburg confirmed that Omicron is spreading quickly.
Tom Wenseleers, an evolutionary biologist at the Catholic University of Leuven in Belgium, estimates that Omicron can infect three to six times as many people as Delta, over the same time period. “That’s a huge advantage for the virus — but not for us,” he told the journal Nature.
当。。。的时候 Delta variant began its rapid spread in the UK, case numbers doubled roughly every five days. Scientists are now carefully monitoring Omicron cases to determine how swiftly the variant is affecting the population of Britain.
On this question, scientists are clear. Evidence indicates that Omicron has an advantage over other variants in bypassing the immune system. “From what we have learned so far, we can be fairly confident that – compared with other variants – Omicron tends to be better able to reinfect people who have been previously infected and received some protection against Covid-19,” said Prof Francois Balloux, director of the Genetics Institute at University College London.
“That is pretty clear and was anticipated from the mutational changes we have pinpointed in its protein structure. These make it more difficult for antibodies to neutralise the virus,.”
This point was backed by Simon Clarke of Reading University. “There is no indication as to how this immune evasion happens, although it can be presumed to be because of decreased antibody binding to Omicron’s mutated spike protein. But decreased T-cell immunity cannot be excluded as a possible contributory factor.”
If previous questions raised fairly worrying responses from scientists, most are more optimistic about the power of jabs to safeguard people from Omicron. “It is extremely unlikely this variant will evade vaccines completely,” said Prof Peter Openshaw of Imperial College London. “The vaccines we have are remarkably effective against a range of other variants but we need more lab and real world data to determine the degree of protection in those vaccinated.”
This is the most difficult question to answer because Omicron has not been known for long enough to determine its ability to cause serious illness. 然而, early evidence does give some grounds for optimism. “The number of cases of Omicron infections does not seem to translate at this stage into the hospitalisation rates we would have expected with similar numbers of cases of Alpha or other variants,” said Balloux.
然而, even if this reduction in serious risk proves correct, it is balanced by the variant’s apparent ability to infect more people.
“We could still get high levels of hospitalisations, and that in turn would put pressure on a nation’s health service.”
再次, it is too early to be sure how the variant might affect the elderly or other members of high-risk groups. 然而, some scientists have voiced concerns. “The big issue is the elderly population,” said Kao.
“Over the past few months, this variant has been circulating in younger age groups, because they’re the ones who are relatively unprotected. 然而, the variant may shift its profile to infect more older people, who we know are more vulnerable to severe infection for the other variants. The reasoning is straightforward. If the variant is able to evade the immune response of young people, then the built-up immunity in the elderly – due to high levels of vaccination combined with natural infection – will be less meaningful. That, obviously, is a real worry.
“Even before Omicron appeared, we were facing the danger that rising numbers of cases could overload the health service. It was so finely tuned. 此外, there is still a prospect of serious seasonal flu returning to increase the burden on hospitals. So any shift towards increased transmissibility, a shifting of age profiles, vaccine evasion, or more severe disease, will put us in a more dangerous situation. Short-term indicators will be helpful but it will probably be a little while before we are able to rule out worse scenarios.”