Findings from trials conducted on lab animals and human tissues have indicated that omicron does not cause as much damage to the lungs, leading to milder disease in those infected.
A consortium of Japanese and American scientists, for instance, found that the damage caused by omicron in mice and hamsters was often limited to the upper airway, which includes the nose, throat, and windpipe.
The animals also lost less weight and were less likely to die, the study found. The scientists were especially struck by the results in Syrian hamsters, a species known to get ‘robustly’ ill with the previous variants.
Dr Michael Diamond, a virus expert at Washington University and a co-author of the study, explained that the reason behind omicron’s reduced severity may be a matter of anatomy. While the level of omicron found in the noses of the animals was the same as when they were infected with another variant, a considerable difference was that the omicron levels in the lungs were only one-tenth or less of the level of others, reported The New York Times.
Roland Eils, a computational biologist at the Berlin Institute of Health, who has studied how coronaviruses infect the airway, also told the newspaper, “It’s fair to say that the idea of a disease that manifests itself primarily in the upper respiratory system is emerging.”
These findings were also corroborated by researchers at the University of Hong Kong, who studied human tissue in Omicron infection cases. They found that the variant grew significantly slower than the earlier strains of the virus, causing reduced severity.
Researchers in the study wrote, “These observations may suggest that Omicron may have reduced clinical severity but such interpretations need to be qualified because the disease severity of Covid-19 is determined not only by virus replication but also by dysregulated innate immune responses.’
It must be noted that neither of the studies has been peer-reviewed yet.
When omicron was first detected in South Africa in November, the sheer number of mutations and its high transmissibility had worried scientists all over. Gradually, however, as cases rose but hospitalisations remained under control, evidence for its milder infection came to the fore.
Data from South Africa, for instance, proved that those infected with the variant were 80% less likely to get hospitalised, than those infected with Delta. Another study by the UK Health and Security found this estimate to be 70%, reported the Daily Mail.