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Just when the world thought it might have COVID-19 under control, the new variant Omicron began spreading through the population faster than any variant seen before. The variant has been reported in 77 countries, though is likely in more, many European countries have re-entered lockdown, and early data suggests that Omicron is magnitudes more infectious than both the original COVID-19 strain and Delta.
Now, new preliminary research, currently under peer-review, is illuminating just how much more transmissible Omicron is, and the mechanisms that allow it to outcompete delta. The study, led by researchers from the LKS Faculty of Medicine at the University of Hong Kong (HKUMed), found that Omicron may multiply a staggering 70 times faster than the Delta variant in human airways, which could account for how rapidly Omicron has spread.
To identify how Omicron is so successful during infection, the research involved the use of lung tissue removed during lung treatment, which is usually discarded. Once the Omicron variant was isolated, the researchers used their tissue cultures to compare how the variant infects cells and how fast it multiplies post-infection, in both lung and bronchus tissues. Omicron was compared against Delta and the SARS-CoV-2 wild-type that began the pandemic in 2020.
They discovered that Omicron was capable of multiplying rapidly in the bronchus tissues, around 70 times faster than Delta in the bronchus. In contrast, it was 10 times slower than wild-type in the lung.
Interestingly, despite the impressive viral load Omicron could produce in a short amount of time, it appears to not increase disease severity, with early data suggesting the new variant may result in less severe disease than other variants. The researchers state this is likely due to disease severity resulting from a number of factors.
“It is important to note that the severity of disease in humans is not determined only by virus replication but also by the host immune response to the infection, which may lead to dysregulation of the innate immune system, i.e. ‘cytokine storm’,” said Dr Michael Chan Chi-wai, who led the team, in a statement.
“It is also noted that, by infecting many more people, a very infectious virus may cause more severe disease and death even though the virus itself may be less pathogenic. Therefore, taken together with our recent studies showing that the Omicron variant can partially escape immunity from vaccines and past infection, the overall threat from Omicron variant is likely to be very significant.”
This research is yet to go through peer-review, so is still preliminary. However, coupled with research published Tuesday suggesting Omicron may be capable of infection with a lower viral dose than both Delta and wild-type, it appears that the mutations Omicron is carrying within the Spike protein enables it to be more transmissible and more infectious than previous COVID-19 strains, allowing it to outcompete them.
However, the threat of "dual infection" from both the Omicron and Delta variant at the same time, leading to the emergence of a new hybrid "super-mutation" variant is low, experts say.
