As India braces for the peak of the third Covid wave with Omicron taking over all other existing variants, scientists are scrambling to find how this heavily-mutated virus spreads so quickly and affects people at an alarmingly high rate, yet spares lungs that have been the key organ being hit by the Covid-19 respiratory disease.
The Omicron variant multiplies about 70 times faster inside human respiratory tract tissue than the Delta variant, according to scientists at the University of Hong Kong.
Omicron also reaches higher levels in the tissue, compared with Delta, 48 hours after infection.
"The finding indicates that mutations in Omicron have sped up the process of entering or replicating (or both) inside the tissue," reports NPR.
However, it is less severe than the previous variants because it does not cause as much damage in the lungs, a spate of studies have suggested.
A study by a consortium of US and Japanese scientists on hamsters and mice, has found those infected with Omicron had less lung damage, lost less weight and were less likely to die than those who had other variants.
The Omicron variant, harbouring up to 36 mutations in spike protein, is known to evade vaccine efficacy.
Another recent study led by researchers at Massachusetts General Hospital (MGH), Harvard and MIT tested blood from people who received the Moderna, Johnson & Johnson, and Pfizer/BioNTech vaccines against a pseudovirus engineered to resemble the Omicron variant.
They included individuals that were both vaccinated recently or had recently taken booster doses, and also had prior SARS-CoV-2 infection.
The findings showed that the neutralisation of Omicron was "undetectable" in most vaccinated individuals.
"The study demonstrates that Omicron drastically escapes vaccine-induced immunity after primary vaccination series with mRNA-1273 (Moderna), BNT162b2 (PfizerBioNTech) or Ad26.COV2.S (Johnson & Johnson/Janssen) and exhibits increased infectivity in vitro, raising the potential for increased transmissibility," said Wilfredo F. Garcia-Beltran, Department of Pathology, MGH at Boston.
"Strikingly, Omicron was 4-fold more infectious than wild type (the original version of the virus) and 2-fold more infectious than Delta," Garcia-Beltran and colleagues wrote in their study.
The data suggests Omicron may be able to infect people at a lower dose than Delta or the original variant.
Inside the lung tissue, Omicron has been reported to be less efficient at infecting cells than delta or the original version of the virus.
"The infection is more focused on the bronchia than the lungs and very fast," Marc Veldhoen, an immunologist at the University of Lisbon, posted on Twitter.
Scientists now need to measure the viral loads inside people's respiratory tracts.
With Delta, people have, on average, 1,000 times more virus particles in their respiratory tracts than with the original variants.
"I want to see what the viral loads look like for Omicron. Samples from people who are actually infected -- that's the gold standard. That's where the action is," said Garcia-Beltran.
On November 26, 2021, the WHO designated the variant B.1.1.529 a variant of concern, named Omicron.
Researchers in South Africa and around the world are conducting studies to better understand many aspects of Omicron.
"All variants of Covid-19, including the Delta variant that is dominant worldwide, can cause severe disease or death, in particular for the most vulnerable people, and thus prevention is always key," according to the WHO.
The most effective steps individuals can take to reduce the spread of the Covid-19 virus is to keep a physical distance of at least 1 metre from others, wear a well-fitting mask, open windows to improve ventilation, avoid poorly ventilated or crowded spaces, keep hands clean, cough or sneeze into a bent elbow or tissue, and get vaccinated when it's their turn.