New Studies Strengthen Belief Omicron Is Less Likely to Damage Lungs | Omicron variant
A growing body of evidence indicates that the Omicron Covid variant is more likely to infect the throat than the lungs, which scientists say could explain why it appears to be more infectious but less fatal than other versions of the virus. Six studies – four published since Christmas Eve – have shown that Omicron does not damage people’s lungs as much as the Delta and other previous variants of Covid. The studies have yet to be evaluated by other scientists.
“The result of all the mutations that differentiate Omicron from previous variants is that it may have altered its ability to infect different types of cells,” said Deenan Pillay, professor of virology at University College London.
“Essentially, it seems to be more capable of infecting the upper respiratory tract – the cells in the throat. It would therefore multiply more easily in cells than in deep lung cells. It’s really preliminary but the studies are going in the same direction.
If the virus produces more cells in the throat, this makes it more transmissible, which would help explain the rapid spread of Omicron. A virus that does infect lung tissue well, on the other hand, will be potentially more dangerous but less transmissible.
Researchers at the University of Liverpool’s Molecular Virology Research Group published a preprint on Boxing Day that shows Omicron causes “less severe disease” in mice, according to Professor James Stewart. The article showed that mice infected with Omicron lose less weight, have a lower viral load, and suffer from less severe pneumonia.
“It’s a piece of the puzzle,” he said. “The animal model suggests the disease is less severe than Delta and the original Wuhan virus. It appears to be cleared more quickly and the animals have recovered faster, which is linked to the clinical data that is reaching us.
“The first indications are that this is good news, but it is not a signal to lower your guard, because if you are clinically vulnerable the consequences are still not great – there are deaths from Omicron. Not everyone can rip off their masks and party.
The Neyts Lab at the University of Louvain in Belgium found similar results in Syrian hamsters, with a lower viral load in the lungs compared to other variants. Professor Johan Neyts said this could be because the virus infects humans better than hamsters, or is more likely to infect the upper respiratory tract, or because it causes less severe illness.
Another pre-print, submitted to Nature last week by researchers in the United States, also found that mice with Omicron lost less weight and had a lower viral load. And researchers at the University of Glasgow’s Virus Research Center have found evidence that Omicron has changed the way it enters the body. Omicron was likely to bypass immunity in people who received two doses of the vaccine, but a booster dose resulted in “partial restoration of immunity.”
Christmas’s extensive research builds on a University of Hong Kong study last month showing fewer Omicron infections in the lungs, and research by Professor Ravi Gupta of the University of Cambridge, including the The team studied blood samples from vaccinated patients. They found Omicron able to escape vaccines, but less able to enter lung cells.
The latest scientific research comes amid a debate over how best to perform home tests. Last week, some scientists suggested that lateral flow tests (LFT) might be more accurate if people took swabs from the throat as well as the nose. Professor Jennifer Rohn of University College London said her experience using LFTs was that she had tested negative using nasal swabs but positive when taking a sample from her throat.
This appeared to be corroborated by a study from South Africa showing that saliva samples subjected to PCR tests were better than nasal swabs at detecting Omicron.
However, Professor Lawrence Young, a virologist at the University of Warwick, said the study was not large enough that any conclusions could be drawn. “This is a small study of patients with acute symptoms who were not hospitalized. On the one hand, this confirms previous studies indicating that saliva testing could be useful as an easier sampling approach to perform. I don’t think this study is meaningful enough to conclude anything about Omicron’s behavior.
The UK Health Safety Agency said there was no indication the rapid tests differed in their ability to detect Omicron or Delta variants, although the tests were continuously monitored by researchers. “All lateral flow devices used by NHS Test and Trace have gone through rigorous validation and have been shown to be very effective at detecting Covid-19 in people,” a spokesperson said. “We are currently seeing a high number of positive lateral flow device tests reported. This means that we are detecting tens of thousands of cases that might otherwise have gone unnoticed. “