Exclusive: study raises hopes that Covid-related damage to sense of smell may be more superficial than previously feared.
The virus that causes Covid-19 does not infect human brain cells, according to a study published in the journal Cell. The findings will raise hopes that the damage caused by Sars-CoV-2 might be more superficial and reversible than previously feared.
The study contradicts earlier research that suggested the virus infects neurons in the membrane that lines the upper recesses of the nose.
This membrane, called the olfactory mucosa, is where the virus first lands when it is inhaled. Within it are olfactory sensory neurons (OSNs), which are responsible for initiating smell sensations. They are tightly entwined with a kind of support cell called sustentacular cells.
In the new study, Belgian and German researchers claim that the virus infects sustentacular cells but not OSNs. “That is just a critical distinction,” said the senior author Peter Mombaerts, who directs the Max Planck Research Unit for Neurogenetics in Frankfurt, Germany. “Once you believe that olfactory neurons can be infected, there is a quick route into the olfactory bulb and then you’re in the brain already.”
The olfactory bulb, at the front of the brain, is where neural input about odours is first processed. If the virus penetrated this structure it could theoretically spread to deeper brain regions where it could do lasting damage – especially since, unlike OSNs, most neurons are not regenerated once lost.
But if the virus only infects the sustentacular cells, then the damage could be less long-lasting.
Both pathways could explain the olfactory dysfunction that afflicts an estimated half of all Covid-19 patients. In one in 10 of those, the loss or change of smell is long-term, perhaps permanent.
Mombaerts says this could be the result of support for the OSNs breaking down, even if they themselves are not infected. They may function below par, or stop functioning altogether, until the sustentacular cells regenerate.
The group has not looked at other neurological symptoms of Covid-19, such as the fatigue and “brain fog” that accompany long Covid.
Nobody doubts that the central nervous system is affected by the disease; the debate concerns whether these effects are due to the virus infecting neurons or some more indirect mechanism, such as an inflammatory response in the blood irrigating the brain – with different implications for prognosis and treatment.
The findings are likely to prove controversial because of the difficulty of studying molecular events unfolding in the moments after infection. Earlier studies made use of animal models, clusters of neural stem cells grown in a dish, and postmortem tissue taken from small numbers of Covid-19 patients. The present study is the largest in Covid-19 patients to date, and it deployed a novel technique for capturing those early events.
Laura Van Gerven, a neurosurgeon at the Catholic University of Leuven in Belgium and another of the paper’s senior authors, adapted a form of skull base surgery to remove tissue from the olfactory mucosa and bulb of Covid-19 patients within about an hour of their death. In 30 of the patients, the researchers were able to detect that the virus was still replicating – meaning the patients had died in the acute, contagious phase of the disease.
“It is unquestionably the most thoroughly done bit of work on human postmortem olfactory Covid tissue,” said Stuart Firestein, a neurobiologist at Columbia University in New York City.
But Firestein said the results did not shed much new light on how Covid-19 causes olfactory dysfunction. “They do not show any OSNs as being damaged or there being fewer of them, or the OSNs near infected sustentacular cells as being different in any way from those not near infected cells,” he said.
Debby Van Riel, a virologist at Erasmus University in Rotterdam, the Netherlands, also praised the study’s rigour, but said the authors’ claim that Sars-CoV-2 does not infect neurons was “pretty bold”.
In only six of the 30 patients was the virus detectable in the olfactory mucosa itself. “Overall the numbers are thus really low to make any strong conclusions,” she said.
But even if the study isn’t the last word on Covid’s brain effects, it does indicate that those dire early reports weren’t either. If its conclusions are borne out, those experiencing Covid-related anosmia or parosmia can be reassured that the virus has not infected their brains, and that future therapies targeting the understudied sustentacular cells could alleviate or cure their condition.

News
Cancer’s “Master Switch” Blocked for Good in Landmark Study
Researchers discovered peptides that permanently block a key cancer protein once thought untreatable, using a new screening method to test their effectiveness inside cells. For the first time, scientists have identified promising drug candidates [...]
AI self-cloning claims: A new frontier or a looming threat?
Chinese scientists claim that some AI models can replicate themselves and protect against shutdown. Has artificial intelligence crossed the so-called red line? Chinese researchers have published two reports on arXiv claiming that some artificial [...]
New Drug Turns Human Blood Into Mosquito-Killing Weapon
Nitisinone, a drug for rare diseases, kills mosquitoes when present in human blood and may become a new tool to fight malaria, offering longer-lasting, environmentally safer effects than ivermectin. Controlling mosquito populations is a [...]
DNA Microscopy Creates 3D Maps of Life From the Inside Out
What if you could take a picture of every gene inside a living organism—not with light, but with DNA itself? Scientists at the University of Chicago have pioneered a revolutionary imaging technique called volumetric DNA microscopy. It builds [...]
Scientists Just Captured the Stunning Process That Shapes Chromosomes
Scientists at EMBL have captured how human chromosomes fold into their signature rod shape during cell division, using a groundbreaking method called LoopTrace. By observing overlapping DNA loops forming in high resolution, they revealed that large [...]
Bird Flu Virus Is Mutating Fast – Scientists Say Our Vaccines May Not Be Enough
H5N1 influenza is evolving rapidly, weakening the effectiveness of existing antibodies and increasing its potential threat to humans. Scientists at UNC Charlotte and MIT used high-performance computational modeling to analyze thousands of viral protein-antibody interactions, revealing [...]
Revolutionary Cancer Vaccine Targets All Solid Tumors
The method triggers immune responses that inhibit melanoma, triple-negative breast cancer, lung carcinoma, and ovarian cancer. Cancer treatment vaccines have been in development since 2010, when the first was approved for prostate cancer, followed [...]
Scientists Uncover Hidden Protein Driving Autoimmune Attacks
Scientists have uncovered a critical piece of the puzzle in autoimmune diseases: a protein that helps release immune response molecules. By studying an ultra-rare condition, researchers identified ArfGAP2 as a key player in immune [...]
Mediterranean neutrino observatory sets new limits on quantum gravity
Quantum gravity is the missing link between general relativity and quantum mechanics, the yet-to-be-discovered key to a unified theory capable of explaining both the infinitely large and the infinitely small. The solution to this [...]
Challenging Previous Beliefs: Japanese Scientists Discover Hidden Protector of Heart
A Japanese research team found that the oxidized form of glutathione (GSSG) may protect heart tissue by modifying a key protein, potentially offering a novel therapeutic approach for ischemic heart failure. A new study [...]
Millions May Have Long COVID – So Why Can’t They Get Diagnosed?
Millions of people in England may be living with Long Covid without even realizing it. A large-scale analysis found that nearly 10% suspect they might have the condition but remain uncertain, often due to [...]
Researchers Reveal What Happens to Your Brain When You Don’t Get Enough Sleep
What if poor sleep was doing more than just making you tired? Researchers have discovered that disrupted sleep in older adults interferes with the brain’s ability to clean out waste, leading to memory problems [...]
How to prevent chronic inflammation from zombie-like cells that accumulate with age
In humans and other multicellular organisms, cells multiply. This defining feature allows embryos to grow into adulthood, and enables the healing of the many bumps, bruises and scrapes along the way. Certain factors can [...]
Breakthrough for long Covid patients who lost sense of smell
A breakthrough nasal surgery has restored the sense of smell for a dozen long Covid patients. Experts at University College London Hospitals NHS Foundation Trust successfully employed a technique typically used for correcting blocked nasal passages, [...]
Scientists Invent Plastic That Can Dissolve In Seawater In Just A Few Hours
Plastic waste and pollution in the sea have been among the most serious environmental problems for decades, causing immense damage to marine life and ecosystems. However, a breakthrough discovery may offer a game-changing solution. [...]
Muscles from the 3D printer
Swiss researchers have developed a method for printing artificial muscles out of silicone. In the future, these could be used on both humans and robots. Swiss researchers have succeeded in printing artificial muscles out [...]